diff --git a/.ado/jobs/desktop.yml b/.ado/jobs/desktop.yml
index 6f5e583a041..7caaad4d46c 100644
--- a/.ado/jobs/desktop.yml
+++ b/.ado/jobs/desktop.yml
@@ -113,7 +113,7 @@ jobs:
                 (FullyQualifiedName!~PreparedJavaScriptSourceTest)
 
           pool: ${{ parameters.AgentPool.Medium }}
-          timeoutInMinutes: 60 # how long to run the job before automatically cancelling
+          timeoutInMinutes: 80 # how long to run the job before automatically cancelling - Issue 13442
           cancelTimeoutInMinutes: 5 # how much time to give 'run always even if cancelled tasks' before killing them
 
           steps:
diff --git a/.ado/jobs/nuget-desktop.yml b/.ado/jobs/nuget-desktop.yml
index 7169dc32b3f..e93822c4bfd 100644
--- a/.ado/jobs/nuget-desktop.yml
+++ b/.ado/jobs/nuget-desktop.yml
@@ -17,19 +17,20 @@ jobs:
       dependsOn:
         - DesktopX64Release
         - DesktopX86Debug
-  
+        - DesktopARM64ECRelease
+
       pool: ${{ parameters.AgentPool.Small }}
       timeoutInMinutes: 30 # how long to run the job before automatically cancelling
       cancelTimeoutInMinutes: 5 # how much time to give 'run always even if cancelled tasks' before killing them
       steps:
         - template: ../templates/checkout-shallow.yml
-  
+
         - template: ../templates/yarn-install.yml
-  
+
         - task: NuGetToolInstaller@1
           inputs:
             versionSpec: ">=5.8.0"
-  
+
         - template: ../templates/prep-and-pack-nuget.yml
           parameters:
             artifactName: Desktop
@@ -39,3 +40,5 @@ jobs:
                 configuration: Release
               - platform: x86
                 configuration: Debug
+              - platform: ARM64EC
+                configuration: Release
diff --git a/change/react-native-windows-3373c57a-968b-415a-b009-f41accdeaf78.json b/change/react-native-windows-3373c57a-968b-415a-b009-f41accdeaf78.json
new file mode 100644
index 00000000000..be8ec288256
--- /dev/null
+++ b/change/react-native-windows-3373c57a-968b-415a-b009-f41accdeaf78.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Update Desktop NUSPEC to use ARM64EC (#13335)",
+  "packageName": "react-native-windows",
+  "email": "julio.rocha@microsoft.com",
+  "dependentChangeType": "patch"
+}
diff --git a/vnext/Scripts/OfficeReact.Win32.nuspec b/vnext/Scripts/OfficeReact.Win32.nuspec
index bbd1a295ca5..dea0abc8b16 100644
--- a/vnext/Scripts/OfficeReact.Win32.nuspec
+++ b/vnext/Scripts/OfficeReact.Win32.nuspec
@@ -15,25 +15,23 @@
   </metadata>
   <files>
 
-    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop.DLL\react-native-win32.*"      target="lib\debug\x86"    exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop.DLL\react-native-win32.*"      target="lib\debug\x64"    exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\ARM64\Debug\React.Windows.Desktop.DLL\react-native-win32.*"    target="lib\debug\ARM64"  exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x86\Release\React.Windows.Desktop.DLL\react-native-win32.*"    target="lib\ship\x86"     exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x64\Release\React.Windows.Desktop.DLL\react-native-win32.*"    target="lib\ship\x64"     exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\ARM64\Release\React.Windows.Desktop.DLL\react-native-win32.*"  target="lib\ship\ARM64"   exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\debug\x86"/>
-    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\debug\x64"/>
-    <file src="$nugetroot$\ARM64\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\debug\ARM64"/>
-    <file src="$nugetroot$\x86\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\ship\x86"/>
-    <file src="$nugetroot$\x64\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\ship\x64"/>
-    <file src="$nugetroot$\ARM64\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\ship\ARM64"/>
+    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop.DLL\react-native-win32.*"          target="lib\debug\x86"      exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop.DLL\react-native-win32.*"          target="lib\debug\x64"      exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\ARM64EC\Debug\React.Windows.Desktop.DLL\react-native-win32.*"      target="lib\debug\ARM64EC"  exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x86\Release\React.Windows.Desktop.DLL\react-native-win32.*"        target="lib\ship\x86"       exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x64\Release\React.Windows.Desktop.DLL\react-native-win32.*"        target="lib\ship\x64"       exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\ARM64EC\Release\React.Windows.Desktop.DLL\react-native-win32.*"    target="lib\ship\ARM64EC"   exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd"       target="lib\debug\x86"/>
+    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd"       target="lib\debug\x64"/>
+    <file src="$nugetroot$\ARM64EC\Debug\React.Windows.Desktop\Microsoft.ReactNative.winmd"   target="lib\debug\ARM64EC"/>
+    <file src="$nugetroot$\x86\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd"     target="lib\ship\x86"/>
+    <file src="$nugetroot$\x64\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd"     target="lib\ship\x64"/>
+    <file src="$nugetroot$\ARM64EC\Release\React.Windows.Desktop\Microsoft.ReactNative.winmd" target="lib\ship\ARM64EC"/>
 
-    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"      target="lib\debug\x86"    exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"      target="lib\debug\x64"    exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\ARM64\Debug\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"    target="lib\debug\ARM64"  exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x86\Release\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"    target="lib\ship\x86"     exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\x64\Release\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"    target="lib\ship\x64"     exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
-    <file src="$nugetroot$\ARM64\Release\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"  target="lib\ship\ARM64"   exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x86\Debug\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"        target="lib\debug\x86"      exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x64\Debug\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"        target="lib\debug\x64"      exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x86\Release\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"      target="lib\ship\x86"       exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
+    <file src="$nugetroot$\x64\Release\React.Windows.Desktop.Test.DLL\React.Windows.Desktop.Test.**"      target="lib\ship\x64"       exclude="**\*.iobj;**\*.ipdb;**\*.exp;**\*.ilk" />
 
     <file src="$nugetroot$\inc\callinvoker\ReactCommon\CallInvoker.h" target="inc\ReactCommon"/>
     <file src="$nugetroot$\inc\callinvoker\ReactCommon\SchedulerPriority.h" target="inc\ReactCommon"/>