diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbfcbdd00a..3de2f68fae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 
 ### Features
 
+- Adds native spans to app start transaction ([#2027](https://github.com/getsentry/sentry-dart/pull/2027))
 - Adds app start spans to first transaction ([#2009](https://github.com/getsentry/sentry-dart/pull/2009))
 
 ### Fixes
diff --git a/flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt b/flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt
index 8d92c9178c..424e51c6b7 100644
--- a/flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt
+++ b/flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt
@@ -23,6 +23,7 @@ import io.sentry.android.core.LoadClass
 import io.sentry.android.core.SentryAndroid
 import io.sentry.android.core.SentryAndroidOptions
 import io.sentry.android.core.performance.AppStartMetrics
+import io.sentry.android.core.performance.TimeSpan
 import io.sentry.protocol.DebugImage
 import io.sentry.protocol.SdkVersion
 import io.sentry.protocol.SentryId
@@ -130,24 +131,66 @@ class SentryFlutterPlugin : FlutterPlugin, MethodCallHandler, ActivityAware {
       return
     }
 
-    val appStartTime = AppStartMetrics.getInstance().appStartTimeSpan.startTimestamp
-    val isColdStart =
-      AppStartMetrics.getInstance().appStartType == AppStartMetrics.AppStartType.COLD
+    val appStartMetrics = AppStartMetrics.getInstance()
+
+    val appStartTimeSpan = appStartMetrics.appStartTimeSpan
+    val appStartTime = appStartTimeSpan.startTimestamp
+    val isColdStart = appStartMetrics.appStartType == AppStartMetrics.AppStartType.COLD
 
     if (appStartTime == null) {
       Log.w("Sentry", "App start won't be sent due to missing appStartTime")
       result.success(null)
     } else {
       val appStartTimeMillis = DateUtils.nanosToMillis(appStartTime.nanoTimestamp().toDouble())
-      val item = mapOf<String, Any?>(
-        "pluginRegistrationTime" to pluginRegistrationTime,
-        "appStartTime" to appStartTimeMillis,
-        "isColdStart" to isColdStart,
-      )
+      val item =
+        mutableMapOf<String, Any?>(
+          "pluginRegistrationTime" to pluginRegistrationTime,
+          "appStartTime" to appStartTimeMillis,
+          "isColdStart" to isColdStart,
+        )
+
+      val androidNativeSpans = mutableMapOf<String, Any?>()
+
+      val processInitSpan =
+        TimeSpan().apply {
+          description = "Process Initialization"
+          setStartUnixTimeMs(appStartTimeSpan.startTimestampMs)
+          setStartedAt(appStartTimeSpan.startUptimeMs)
+          setStoppedAt(appStartMetrics.classLoadedUptimeMs)
+        }
+      processInitSpan.addToMap(androidNativeSpans)
+
+      val applicationOnCreateSpan = appStartMetrics.applicationOnCreateTimeSpan
+      applicationOnCreateSpan.addToMap(androidNativeSpans)
+
+      val contentProviderSpans = appStartMetrics.contentProviderOnCreateTimeSpans
+      contentProviderSpans.forEach { span ->
+        span.addToMap(androidNativeSpans)
+      }
+
+      appStartMetrics.activityLifecycleTimeSpans.forEach { span ->
+        span.onCreate.addToMap(androidNativeSpans)
+        span.onStart.addToMap(androidNativeSpans)
+      }
+
+      item["nativeSpanTimes"] = androidNativeSpans
+
       result.success(item)
     }
   }
 
+  private fun TimeSpan.addToMap(map: MutableMap<String, Any?>) {
+    if (startTimestamp == null) return
+
+    description?.let { description ->
+      map[description] =
+        mapOf<String, Any?>(
+          "startTimestampMsSinceEpoch" to startTimestampMs,
+          "stopTimestampMsSinceEpoch" to projectedStopTimestampMs,
+        )
+    }
+  }
+
   private fun beginNativeFrames(result: Result) {
     if (!sentryFlutter.autoPerformanceTracingEnabled) {
       result.success(null)
diff --git a/flutter/example/android/build.gradle b/flutter/example/android/build.gradle
index 50bb21eda7..693111bbb3 100644
--- a/flutter/example/android/build.gradle
+++ b/flutter/example/android/build.gradle
@@ -7,7 +7,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'io.sentry:sentry-android-gradle-plugin:4.2.0'
+        classpath 'io.sentry:sentry-android-gradle-plugin:4.5.0'
         classpath 'com.android.tools.build:gradle:7.2.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         classpath 'io.github.howardpang:androidNativeBundle:1.1.3'
@@ -32,4 +32,3 @@ subprojects {
 tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }
-
diff --git a/flutter/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme b/flutter/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
index 0fa7c24eb1..fee8e19903 100644
--- a/flutter/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
+++ b/flutter/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1430"
+   LastUpgradeVersion = "1510"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
diff --git a/flutter/ios/Classes/SentryFlutterPluginApple.swift b/flutter/ios/Classes/SentryFlutterPluginApple.swift
index 97a10c3324..fc8fb42f9c 100644
--- a/flutter/ios/Classes/SentryFlutterPluginApple.swift
+++ b/flutter/ios/Classes/SentryFlutterPluginApple.swift
@@ -379,6 +379,19 @@ public class SentryFlutterPluginApple: NSObject, FlutterPlugin {
         return
     }
 
+    struct TimeSpan {
+        var startTimestampMsSinceEpoch: NSNumber
+        var stopTimestampMsSinceEpoch: NSNumber
+        var description: String
+
+        func addToMap(_ map: inout [String: Any]) {
+            map[description] = [
+                "startTimestampMsSinceEpoch": startTimestampMsSinceEpoch,
+                "stopTimestampMsSinceEpoch": stopTimestampMsSinceEpoch
+            ]
+        }
+    }
+
     private func fetchNativeAppStart(result: @escaping FlutterResult) {
         #if os(iOS) || os(tvOS)
         guard let appStartMeasurement = PrivateSentrySDKOnly.appStartMeasurement else {
@@ -387,13 +400,53 @@ public class SentryFlutterPluginApple: NSObject, FlutterPlugin {
             return
         }
 
+        var nativeSpanTimes: [String: Any] = [:]
+
+        let appStartTimeMs = appStartMeasurement.appStartTimestamp.timeIntervalSince1970.toMilliseconds()
+        let runtimeInitTimeMs = appStartMeasurement.runtimeInitTimestamp.timeIntervalSince1970.toMilliseconds()
+        let moduleInitializationTimeMs =
+            appStartMeasurement.moduleInitializationTimestamp.timeIntervalSince1970.toMilliseconds()
+        let sdkStartTimeMs = appStartMeasurement.sdkStartTimestamp.timeIntervalSince1970.toMilliseconds()
+
+        if !appStartMeasurement.isPreWarmed {
+            let preRuntimeInitDescription = "Pre Runtime Init"
+            let preRuntimeInitSpan = TimeSpan(
+                startTimestampMsSinceEpoch: NSNumber(value: appStartTimeMs),
+                stopTimestampMsSinceEpoch: NSNumber(value: runtimeInitTimeMs),
+                description: preRuntimeInitDescription
+            )
+            preRuntimeInitSpan.addToMap(&nativeSpanTimes)
+
+            let moduleInitializationDescription = "Runtime init to Pre Main initializers"
+            let moduleInitializationSpan = TimeSpan(
+                startTimestampMsSinceEpoch: NSNumber(value: runtimeInitTimeMs),
+                stopTimestampMsSinceEpoch: NSNumber(value: moduleInitializationTimeMs),
+                description: moduleInitializationDescription
+            )
+            moduleInitializationSpan.addToMap(&nativeSpanTimes)
+        }
+
+        let uiKitInitDescription = "UIKit init"
+        let uiKitInitSpan = TimeSpan(
+            startTimestampMsSinceEpoch: NSNumber(value: moduleInitializationTimeMs),
+            stopTimestampMsSinceEpoch: NSNumber(value: sdkStartTimeMs),
+            description: uiKitInitDescription
+        )
+        uiKitInitSpan.addToMap(&nativeSpanTimes)
+
+        // Info: We don't have access to didFinishLaunchingTimestamp,
+        // On HybridSDKs, the Cocoa SDK misses the didFinishLaunchNotification and the
+        // didBecomeVisibleNotification. Therefore, we can't set the
+        // didFinishLaunchingTimestamp
+
         let appStartTime = appStartMeasurement.appStartTimestamp.timeIntervalSince1970 * 1000
         let isColdStart = appStartMeasurement.type == .cold
 
         let item: [String: Any] = [
             "pluginRegistrationTime": SentryFlutterPluginApple.pluginRegistrationTime,
             "appStartTime": appStartTime,
-            "isColdStart": isColdStart
+            "isColdStart": isColdStart,
+            "nativeSpanTimes": nativeSpanTimes
         ]
 
         result(item)
@@ -601,3 +654,9 @@ public class SentryFlutterPluginApple: NSObject, FlutterPlugin {
 }
 
 // swiftlint:enable function_body_length
+
+private extension TimeInterval {
+    func toMilliseconds() -> Int64 {
+        return Int64(self * 1000)
+    }
+}
diff --git a/flutter/lib/src/event_processor/native_app_start_event_processor.dart b/flutter/lib/src/event_processor/native_app_start_event_processor.dart
index 57e2eb4ed6..f8ea23b265 100644
--- a/flutter/lib/src/event_processor/native_app_start_event_processor.dart
+++ b/flutter/lib/src/event_processor/native_app_start_event_processor.dart
@@ -42,7 +42,6 @@ class NativeAppStartEventProcessor implements EventProcessor {
     }
 
     final measurement = appStartInfo?.toMeasurement();
-
     if (measurement != null) {
       event.measurements[measurement.name] = measurement;
       _native.didAddAppStartMeasurement = true;
@@ -72,6 +71,8 @@ class NativeAppStartEventProcessor implements EventProcessor {
         startTimestamp: appStartInfo.start,
         endTimestamp: appStartEnd);
 
+    await _attachNativeSpans(appStartInfo, transaction, appStartSpan);
+
     final pluginRegistrationSpan = await _createAndFinishSpan(
         tracer: transaction,
         operation: appStartInfo.appStartTypeOperation,
@@ -81,14 +82,14 @@ class NativeAppStartEventProcessor implements EventProcessor {
         startTimestamp: appStartInfo.start,
         endTimestamp: appStartInfo.pluginRegistration);
 
-    final mainIsolateSetupSpan = await _createAndFinishSpan(
+    final sentrySetupSpan = await _createAndFinishSpan(
         tracer: transaction,
         operation: appStartInfo.appStartTypeOperation,
-        description: appStartInfo.mainIsolateSetupDescription,
+        description: appStartInfo.sentrySetupDescription,
         parentSpanId: appStartSpan.context.spanId,
         traceId: transactionTraceId,
         startTimestamp: appStartInfo.pluginRegistration,
-        endTimestamp: appStartInfo.mainIsolateStart);
+        endTimestamp: appStartInfo.sentrySetupStart);
 
     final firstFrameRenderSpan = await _createAndFinishSpan(
         tracer: transaction,
@@ -96,17 +97,39 @@ class NativeAppStartEventProcessor implements EventProcessor {
         description: appStartInfo.firstFrameRenderDescription,
         parentSpanId: appStartSpan.context.spanId,
         traceId: transactionTraceId,
-        startTimestamp: appStartInfo.mainIsolateStart,
+        startTimestamp: appStartInfo.sentrySetupStart,
         endTimestamp: appStartEnd);
 
     transaction.children.addAll([
       appStartSpan,
       pluginRegistrationSpan,
-      mainIsolateSetupSpan,
+      sentrySetupSpan,
       firstFrameRenderSpan
     ]);
   }
 
+  Future<void> _attachNativeSpans(AppStartInfo appStartInfo,
+      SentryTracer transaction, SentrySpan parent) async {
+    await Future.forEach<TimeSpan>(appStartInfo.nativeSpanTimes,
+        (timeSpan) async {
+      try {
+        final span = await _createAndFinishSpan(
+            tracer: transaction,
+            operation: appStartInfo.appStartTypeOperation,
+            description: timeSpan.description,
+            parentSpanId: parent.context.spanId,
+            traceId: transaction.context.traceId,
+            startTimestamp: timeSpan.start,
+            endTimestamp: timeSpan.end);
+        span.data.putIfAbsent('native', () => true);
+        transaction.children.add(span);
+      } catch (e) {
+        _hub.options.logger(SentryLevel.warning,
+            'Failed to attach native span to app start transaction: $e');
+      }
+    });
+  }
+
   Future<SentrySpan> _createAndFinishSpan({
     required SentryTracer tracer,
     required String operation,
diff --git a/flutter/lib/src/integrations/native_app_start_integration.dart b/flutter/lib/src/integrations/native_app_start_integration.dart
index 7b015220a9..13ca865422 100644
--- a/flutter/lib/src/integrations/native_app_start_integration.dart
+++ b/flutter/lib/src/integrations/native_app_start_integration.dart
@@ -10,10 +10,13 @@ import '../event_processor/native_app_start_event_processor.dart';
 /// Integration which handles communication with native frameworks in order to
 /// enrich [SentryTransaction] objects with app start data for mobile vitals.
 class NativeAppStartIntegration extends Integration<SentryFlutterOptions> {
-  NativeAppStartIntegration(this._native, this._frameCallbackHandler);
+  NativeAppStartIntegration(this._native, this._frameCallbackHandler,
+      {Hub? hub})
+      : _hub = hub ?? HubAdapter();
 
   final SentryNative _native;
   final FrameCallbackHandler _frameCallbackHandler;
+  final Hub _hub;
 
   /// Timeout duration to wait for the app start info to be fetched.
   static const _timeoutDuration = Duration(seconds: 30);
@@ -55,13 +58,15 @@ class NativeAppStartIntegration extends Integration<SentryFlutterOptions> {
   @override
   void call(Hub hub, SentryFlutterOptions options) {
     if (isIntegrationTest) {
-      final appStartInfo = AppStartInfo(AppStartType.cold,
-          start: DateTime.now(),
-          end: DateTime.now().add(const Duration(milliseconds: 100)),
-          pluginRegistration:
-              DateTime.now().add(const Duration(milliseconds: 50)),
-          mainIsolateStart:
-              DateTime.now().add(const Duration(milliseconds: 60)));
+      final appStartInfo = AppStartInfo(
+        AppStartType.cold,
+        start: DateTime.now(),
+        end: DateTime.now().add(const Duration(milliseconds: 100)),
+        pluginRegistration:
+            DateTime.now().add(const Duration(milliseconds: 50)),
+        sentrySetupStart: DateTime.now().add(const Duration(milliseconds: 60)),
+        nativeSpanTimes: [],
+      );
       setAppStartInfo(appStartInfo);
       return;
     }
@@ -77,7 +82,12 @@ class NativeAppStartIntegration extends Integration<SentryFlutterOptions> {
         return;
       }
 
-      final mainIsolateStartDateTime = SentryFlutter.mainIsolateStartTime;
+      final sentrySetupStartDateTime = SentryFlutter.sentrySetupStartTime;
+      if (sentrySetupStartDateTime == null) {
+        setAppStartInfo(null);
+        return;
+      }
+
       final appStartDateTime = DateTime.fromMillisecondsSinceEpoch(
           nativeAppStart.appStartTime.toInt());
       final pluginRegistrationDateTime = DateTime.fromMillisecondsSinceEpoch(
@@ -106,12 +116,37 @@ class NativeAppStartIntegration extends Integration<SentryFlutterOptions> {
         }
       }
 
+      List<TimeSpan> nativeSpanTimes = [];
+      for (final entry in nativeAppStart.nativeSpanTimes.entries) {
+        try {
+          final startTimestampMs =
+              entry.value['startTimestampMsSinceEpoch'] as int;
+          final endTimestampMs =
+              entry.value['stopTimestampMsSinceEpoch'] as int;
+          nativeSpanTimes.add(TimeSpan(
+            start: DateTime.fromMillisecondsSinceEpoch(startTimestampMs),
+            end: DateTime.fromMillisecondsSinceEpoch(endTimestampMs),
+            description: entry.key as String,
+          ));
+        } catch (e) {
+          // ignore: invalid_use_of_internal_member
+          _hub.options.logger(
+              SentryLevel.warning, 'Failed to parse native span times: $e');
+          continue;
+        }
+      }
+
+      // We want to sort because the native spans are not guaranteed to be in order.
+      // Performance wise this won't affect us since the native span amount is very low.
+      nativeSpanTimes.sort((a, b) => a.start.compareTo(b.start));
+
       final appStartInfo = AppStartInfo(
           nativeAppStart.isColdStart ? AppStartType.cold : AppStartType.warm,
           start: appStartDateTime,
           end: appStartEndDateTime,
           pluginRegistration: pluginRegistrationDateTime,
-          mainIsolateStart: mainIsolateStartDateTime);
+          sentrySetupStart: sentrySetupStartDateTime,
+          nativeSpanTimes: nativeSpanTimes);
 
       setAppStartInfo(appStartInfo);
     });
@@ -129,19 +164,21 @@ class AppStartInfo {
     this.type, {
     required this.start,
     required this.pluginRegistration,
-    required this.mainIsolateStart,
+    required this.sentrySetupStart,
+    required this.nativeSpanTimes,
     this.end,
   });
 
   final AppStartType type;
   final DateTime start;
+  final List<TimeSpan> nativeSpanTimes;
 
   // We allow the end to be null, since it might be set at a later time
   // with setAppStartEnd when autoAppStart is disabled
   DateTime? end;
 
   final DateTime pluginRegistration;
-  final DateTime mainIsolateStart;
+  final DateTime sentrySetupStart;
 
   Duration? get duration => end?.difference(start);
 
@@ -160,6 +197,14 @@ class AppStartInfo {
   String get appStartTypeDescription =>
       type == AppStartType.cold ? 'Cold start' : 'Warm start';
   final pluginRegistrationDescription = 'App start to plugin registration';
-  final mainIsolateSetupDescription = 'Main isolate setup';
+  final sentrySetupDescription = 'Before Sentry Init Setup';
   final firstFrameRenderDescription = 'First frame render';
 }
+
+class TimeSpan {
+  TimeSpan({required this.start, required this.end, required this.description});
+
+  final DateTime start;
+  final DateTime end;
+  final String description;
+}
diff --git a/flutter/lib/src/native/sentry_native.dart b/flutter/lib/src/native/sentry_native.dart
index 893c55d6bc..d8d9c5a964 100644
--- a/flutter/lib/src/native/sentry_native.dart
+++ b/flutter/lib/src/native/sentry_native.dart
@@ -137,17 +137,20 @@ class NativeAppStart {
   NativeAppStart(
       {required this.appStartTime,
       required this.pluginRegistrationTime,
-      required this.isColdStart});
+      required this.isColdStart,
+      required this.nativeSpanTimes});
 
   double appStartTime;
   int pluginRegistrationTime;
   bool isColdStart;
+  Map<dynamic, dynamic> nativeSpanTimes;
 
   factory NativeAppStart.fromJson(Map<String, dynamic> json) {
     return NativeAppStart(
       appStartTime: json['appStartTime'] as double,
       pluginRegistrationTime: json['pluginRegistrationTime'] as int,
       isColdStart: json['isColdStart'] as bool,
+      nativeSpanTimes: json['nativeSpanTimes'] as Map<dynamic, dynamic>,
     );
   }
 }
diff --git a/flutter/lib/src/sentry_flutter.dart b/flutter/lib/src/sentry_flutter.dart
index 9b0792c7e3..e0d4415de5 100644
--- a/flutter/lib/src/sentry_flutter.dart
+++ b/flutter/lib/src/sentry_flutter.dart
@@ -34,10 +34,10 @@ typedef FlutterOptionsConfiguration = FutureOr<void> Function(
 mixin SentryFlutter {
   static const _channel = MethodChannel('sentry_flutter');
 
-  /// Represents the time when the main isolate is set up and ready to execute.
+  /// Represents the time when the Sentry init set up has started.
   @internal
   // ignore: invalid_use_of_internal_member
-  static DateTime mainIsolateStartTime = getUtcDateTime();
+  static DateTime? sentrySetupStartTime;
 
   static Future<void> init(
     FlutterOptionsConfiguration optionsConfiguration, {
@@ -48,6 +48,9 @@ mixin SentryFlutter {
   }) async {
     final flutterOptions = SentryFlutterOptions();
 
+    // ignore: invalid_use_of_internal_member
+    sentrySetupStartTime ??= flutterOptions.clock();
+
     if (platformChecker != null) {
       flutterOptions.platformChecker = platformChecker;
     }
diff --git a/flutter/test/integrations/native_app_start_integration_test.dart b/flutter/test/integrations/native_app_start_integration_test.dart
index 0ebc3cb4c2..ce555ceb9d 100644
--- a/flutter/test/integrations/native_app_start_integration_test.dart
+++ b/flutter/test/integrations/native_app_start_integration_test.dart
@@ -25,7 +25,10 @@ void main() {
     test('native app start measurement added to first transaction', () async {
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(10);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
 
@@ -45,7 +48,10 @@ void main() {
         () async {
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(10);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
 
@@ -65,7 +71,10 @@ void main() {
     test('measurements appended', () async {
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(10);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
       final measurement = SentryMeasurement.warmAppStart(Duration(seconds: 1));
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
@@ -88,7 +97,10 @@ void main() {
     test('native app start measurement not added if more than 60s', () async {
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(60001);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
 
@@ -106,7 +118,10 @@ void main() {
         () async {
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(10);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
 
@@ -120,7 +135,10 @@ void main() {
         () async {
       fixture.options.autoAppStart = false;
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
 
@@ -140,7 +158,10 @@ void main() {
         () async {
       fixture.options.autoAppStart = false;
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
       SentryFlutter.native = fixture.native;
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
@@ -166,16 +187,15 @@ void main() {
           (element) =>
               element.context.description ==
               appStartInfo!.pluginRegistrationDescription);
-      final mainIsolateSetupSpan = enriched.spans.firstWhereOrNull((element) =>
-          element.context.description ==
-          appStartInfo!.mainIsolateSetupDescription);
+      final sentrySetupSpan = enriched.spans.firstWhereOrNull((element) =>
+          element.context.description == appStartInfo!.sentrySetupDescription);
       final firstFrameRenderSpan = enriched.spans.firstWhereOrNull((element) =>
           element.context.description ==
           appStartInfo!.firstFrameRenderDescription);
 
       expect(appStartSpan, isNotNull);
       expect(pluginRegistrationSpan, isNotNull);
-      expect(mainIsolateSetupSpan, isNotNull);
+      expect(sentrySetupSpan, isNotNull);
       expect(firstFrameRenderSpan, isNotNull);
     });
   });
@@ -183,11 +203,43 @@ void main() {
   group('App start spans', () {
     late SentrySpan? coldStartSpan,
         pluginRegistrationSpan,
-        mainIsolateSetupSpan,
+        sentrySetupSpan,
         firstFrameRenderSpan;
     // ignore: invalid_use_of_internal_member
     late SentryTracer tracer;
     late Fixture fixture;
+    late SentryTransaction enriched;
+
+    final validNativeSpanTimes = {
+      'correct span description': {
+        'startTimestampMsSinceEpoch': 1,
+        'stopTimestampMsSinceEpoch': 2,
+      },
+      'correct span description 2': {
+        'startTimestampMsSinceEpoch': 4,
+        'stopTimestampMsSinceEpoch': 6,
+      },
+      'correct span description 3': {
+        'startTimestampMsSinceEpoch': 3,
+        'stopTimestampMsSinceEpoch': 4,
+      },
+    };
+
+    final invalidNativeSpanTimes = {
+      'failing span with null timestamp': {
+        'startTimestampMsSinceEpoch': null,
+        'stopTimestampMsSinceEpoch': 3,
+      },
+      'failing span with string timestamp': {
+        'startTimestampMsSinceEpoch': '1',
+        'stopTimestampMsSinceEpoch': 3,
+      },
+    };
+
+    final allNativeSpanTimes = {
+      ...validNativeSpanTimes,
+      ...invalidNativeSpanTimes,
+    };
 
     setUp(() async {
       TestWidgetsFlutterBinding.ensureInitialized();
@@ -197,9 +249,12 @@ void main() {
 
       fixture.native.appStartEnd = DateTime.fromMillisecondsSinceEpoch(50);
       fixture.binding.nativeAppStart = NativeAppStart(
-          appStartTime: 0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: allNativeSpanTimes);
       // dartLoadingEnd needs to be set after engine end (see MockNativeChannel)
-      SentryFlutter.mainIsolateStartTime =
+      SentryFlutter.sentrySetupStartTime =
           DateTime.fromMillisecondsSinceEpoch(15);
 
       fixture.getNativeAppStartIntegration().call(fixture.hub, fixture.options);
@@ -207,7 +262,7 @@ void main() {
       final processor = fixture.options.eventProcessors.first;
       tracer = fixture.createTracer();
       final transaction = SentryTransaction(tracer);
-      final enriched =
+      enriched =
           await processor.apply(transaction, Hint()) as SentryTransaction;
 
       final appStartInfo = await NativeAppStartIntegration.getAppStartInfo();
@@ -217,18 +272,68 @@ void main() {
       pluginRegistrationSpan = enriched.spans.firstWhereOrNull((element) =>
           element.context.description ==
           appStartInfo?.pluginRegistrationDescription);
-      mainIsolateSetupSpan = enriched.spans.firstWhereOrNull((element) =>
-          element.context.description ==
-          appStartInfo?.mainIsolateSetupDescription);
+      sentrySetupSpan = enriched.spans.firstWhereOrNull((element) =>
+          element.context.description == appStartInfo?.sentrySetupDescription);
       firstFrameRenderSpan = enriched.spans.firstWhereOrNull((element) =>
           element.context.description ==
           appStartInfo?.firstFrameRenderDescription);
     });
 
+    test('native app start spans not added to following transactions',
+        () async {
+      final processor = fixture.options.eventProcessors.first;
+
+      final transaction = SentryTransaction(fixture.createTracer());
+
+      final secondEnriched =
+          await processor.apply(transaction, Hint()) as SentryTransaction;
+
+      expect(secondEnriched.spans.length, 0);
+    });
+
+    test('includes only valid native spans', () async {
+      final spans =
+          enriched.spans.where((element) => element.data['native'] == true);
+
+      expect(spans.length, validNativeSpanTimes.length);
+
+      for (final span in spans) {
+        final validSpan = validNativeSpanTimes[span.context.description];
+        expect(validSpan, isNotNull);
+        expect(
+            span.startTimestamp,
+            DateTime.fromMillisecondsSinceEpoch(
+                    validSpan!['startTimestampMsSinceEpoch']!)
+                .toUtc());
+        expect(
+            span.endTimestamp,
+            DateTime.fromMillisecondsSinceEpoch(
+                    validSpan['stopTimestampMsSinceEpoch']!)
+                .toUtc());
+      }
+    });
+
+    test('are correctly ordered', () async {
+      final spans =
+          enriched.spans.where((element) => element.data['native'] == true);
+
+      final orderedSpans = spans.toList()
+        ..sort((a, b) => a.startTimestamp.compareTo(b.startTimestamp));
+
+      expect(spans, orderedEquals(orderedSpans));
+    });
+
+    test('ignores invalid spans', () async {
+      final spans =
+          enriched.spans.where((element) => element.data['native'] == true);
+
+      expect(spans, isNot(contains('failing span')));
+    });
+
     test('are added by event processor', () async {
       expect(coldStartSpan, isNotNull);
       expect(pluginRegistrationSpan, isNotNull);
-      expect(mainIsolateSetupSpan, isNotNull);
+      expect(sentrySetupSpan, isNotNull);
       expect(firstFrameRenderSpan, isNotNull);
     });
 
@@ -236,7 +341,7 @@ void main() {
       const op = 'app.start.cold';
       expect(coldStartSpan?.context.operation, op);
       expect(pluginRegistrationSpan?.context.operation, op);
-      expect(mainIsolateSetupSpan?.context.operation, op);
+      expect(sentrySetupSpan?.context.operation, op);
       expect(firstFrameRenderSpan?.context.operation, op);
     });
 
@@ -244,8 +349,8 @@ void main() {
       expect(coldStartSpan?.context.parentSpanId, tracer.context.spanId);
       expect(pluginRegistrationSpan?.context.parentSpanId,
           coldStartSpan?.context.spanId);
-      expect(mainIsolateSetupSpan?.context.parentSpanId,
-          coldStartSpan?.context.spanId);
+      expect(
+          sentrySetupSpan?.context.parentSpanId, coldStartSpan?.context.spanId);
       expect(firstFrameRenderSpan?.context.parentSpanId,
           coldStartSpan?.context.spanId);
     });
@@ -254,7 +359,7 @@ void main() {
       final traceId = tracer.context.traceId;
       expect(coldStartSpan?.context.traceId, traceId);
       expect(pluginRegistrationSpan?.context.traceId, traceId);
-      expect(mainIsolateSetupSpan?.context.traceId, traceId);
+      expect(sentrySetupSpan?.context.traceId, traceId);
       expect(firstFrameRenderSpan?.context.traceId, traceId);
     });
 
@@ -264,10 +369,10 @@ void main() {
           .toUtc();
       expect(coldStartSpan?.startTimestamp, appStartTime);
       expect(pluginRegistrationSpan?.startTimestamp, appStartTime);
-      expect(mainIsolateSetupSpan?.startTimestamp,
+      expect(sentrySetupSpan?.startTimestamp,
           pluginRegistrationSpan?.endTimestamp);
-      expect(firstFrameRenderSpan?.startTimestamp,
-          mainIsolateSetupSpan?.endTimestamp);
+      expect(
+          firstFrameRenderSpan?.startTimestamp, sentrySetupSpan?.endTimestamp);
     });
 
     test('have correct endTimestamp', () async {
@@ -276,8 +381,8 @@ void main() {
           .toUtc();
       expect(coldStartSpan?.endTimestamp, fixture.native.appStartEnd?.toUtc());
       expect(pluginRegistrationSpan?.endTimestamp, engineReadyEndtime);
-      expect(mainIsolateSetupSpan?.endTimestamp,
-          SentryFlutter.mainIsolateStartTime.toUtc());
+      expect(sentrySetupSpan?.endTimestamp,
+          SentryFlutter.sentrySetupStartTime?.toUtc());
       expect(firstFrameRenderSpan?.endTimestamp, coldStartSpan?.endTimestamp);
     });
   });
@@ -292,6 +397,7 @@ class Fixture {
   Fixture() {
     native.reset();
     when(hub.options).thenReturn(options);
+    SentryFlutter.sentrySetupStartTime = DateTime.now().toUtc();
   }
 
   NativeAppStartIntegration getNativeAppStartIntegration() {
diff --git a/flutter/test/navigation/sentry_display_widget_test.dart b/flutter/test/navigation/sentry_display_widget_test.dart
index 6a0e912d5e..2cafb706d5 100644
--- a/flutter/test/navigation/sentry_display_widget_test.dart
+++ b/flutter/test/navigation/sentry_display_widget_test.dart
@@ -62,7 +62,8 @@ void main() {
       start: getUtcDateTime().add(Duration(seconds: 1)),
       end: getUtcDateTime().add(Duration(seconds: 2)),
       pluginRegistration: getUtcDateTime().add(Duration(seconds: 3)),
-      mainIsolateStart: getUtcDateTime().add(Duration(seconds: 4)),
+      sentrySetupStart: getUtcDateTime().add(Duration(seconds: 4)),
+      nativeSpanTimes: [],
     );
     NativeAppStartIntegration.setAppStartInfo(appStartInfo);
 
diff --git a/flutter/test/sentry_native_channel_test.dart b/flutter/test/sentry_native_channel_test.dart
index 4d5e539838..a8debae3e4 100644
--- a/flutter/test/sentry_native_channel_test.dart
+++ b/flutter/test/sentry_native_channel_test.dart
@@ -23,6 +23,8 @@ void main() {
         'pluginRegistrationTime': 1,
         'appStartTime': 0.1,
         'isColdStart': true,
+        // ignore: inference_failure_on_collection_literal
+        'nativeSpanTimes': {},
       };
       final future = Future.value(map);
 
diff --git a/flutter/test/sentry_native_test.dart b/flutter/test/sentry_native_test.dart
index 341c8aaad8..92b7c2e28e 100644
--- a/flutter/test/sentry_native_test.dart
+++ b/flutter/test/sentry_native_test.dart
@@ -1,5 +1,4 @@
 @TestOn('vm')
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:sentry_flutter/sentry_flutter.dart';
 import 'package:sentry_flutter/src/native/sentry_native.dart';
@@ -17,7 +16,10 @@ void main() {
 
     test('fetchNativeAppStart sets didFetchAppStart', () async {
       final nativeAppStart = NativeAppStart(
-          appStartTime: 0.0, pluginRegistrationTime: 10, isColdStart: true);
+          appStartTime: 0.0,
+          pluginRegistrationTime: 10,
+          isColdStart: true,
+          nativeSpanTimes: {});
       channel.nativeAppStart = nativeAppStart;
 
       expect(sut.didFetchAppStart, false);
diff --git a/flutter/test/sentry_navigator_observer_test.dart b/flutter/test/sentry_navigator_observer_test.dart
index 94ce9e6107..e2b1488cca 100644
--- a/flutter/test/sentry_navigator_observer_test.dart
+++ b/flutter/test/sentry_navigator_observer_test.dart
@@ -502,7 +502,8 @@ void main() {
           start: DateTime.now().add(const Duration(seconds: 1)),
           end: DateTime.now().add(const Duration(seconds: 2)),
           pluginRegistration: DateTime.now().add(const Duration(seconds: 3)),
-          mainIsolateStart: DateTime.now().add(const Duration(seconds: 4)),
+          sentrySetupStart: DateTime.now().add(const Duration(seconds: 4)),
+          nativeSpanTimes: [],
         ),
       );