diff --git a/addon/README.md b/addon/README.md
index a561172d..fa2b5ffa 100644
--- a/addon/README.md
+++ b/addon/README.md
@@ -189,6 +189,13 @@ module.exports = function (defaults) {
            * removes the CSS for the test-container (where the app and components are rendered to)
            */
           disableContainerStyles: true,
+          /**
+           * default: 'qunit-default'
+           * options: 'qunit-default' | 'ember'
+           * 
+           * Sets the theme for the Web UI of the test runner. Use a different value to disable loading any theme, allowing you to provide your own external one.
+           */
+          theme: 'qunit-default',
         },
       },
     },
diff --git a/addon/package.json b/addon/package.json
index fedb21be..eafbb24a 100644
--- a/addon/package.json
+++ b/addon/package.json
@@ -43,7 +43,8 @@
   "dependencies": {
     "@embroider/addon-shim": "^1.8.6",
     "@embroider/macros": "^1.13.1",
-    "ember-cli-test-loader": "^3.1.0"
+    "ember-cli-test-loader": "^3.1.0",
+    "qunit-theme-ember": "^1.0.0"
   },
   "devDependencies": {
     "@babel/core": "^7.23.2",
diff --git a/addon/src/index.js b/addon/src/index.js
index afe79323..728604ba 100644
--- a/addon/src/index.js
+++ b/addon/src/index.js
@@ -1,12 +1,27 @@
 /* globals Testem */
-import 'qunit/qunit/qunit.css';
-
 import { macroCondition, getOwnConfig, importSync } from '@embroider/macros';
 
+/**
+ * Load qunit-default theme by default, if no custom theme is specified.
+ */
+if (
+  macroCondition(
+    getOwnConfig()?.theme === undefined ||
+      getOwnConfig()?.theme === 'qunit-default' ||
+      getOwnConfig()?.theme === 'ember'
+  )
+) {
+  importSync('qunit/qunit/qunit.css');
+}
+
 if (macroCondition(!getOwnConfig()?.disableContainerStyles)) {
   importSync('./test-container-styles.css');
 }
 
+if (macroCondition(getOwnConfig()?.theme === 'ember')) {
+  importSync('qunit-theme-ember/qunit.css');
+}
+
 export { default as QUnitAdapter, nonTestDoneCallback } from './adapter';
 export { loadTests } from './test-loader';
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9fd1fed7..2a1419bf 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -19,6 +19,9 @@ importers:
       ember-cli-test-loader:
         specifier: ^3.1.0
         version: 3.1.0
+      qunit-theme-ember:
+        specifier: ^1.0.0
+        version: 1.0.0
     devDependencies:
       '@babel/core':
         specifier: ^7.23.2
@@ -11398,6 +11401,10 @@ packages:
       - supports-color
     dev: true
 
+  /qunit-theme-ember@1.0.0:
+    resolution: {integrity: sha512-vdMVVo6ecdCkWttMTKeyq1ZTLGHcA6zdze2zhguNuc3ritlJMhOXY5RDseqazOwqZVfCg3rtlmL3fMUyIzUyFQ==}
+    dev: false
+
   /qunit@2.20.0:
     resolution: {integrity: sha512-N8Fp1J55waE+QG1KwX2LOyqulZUToRrrPBqDOfYfuAMkEglFL15uwvmH1P4Tq/omQ/mGbBI8PEB3PhIfvUb+jg==}
     engines: {node: '>=10'}
@@ -13906,6 +13913,7 @@ packages:
       ember-cli-test-loader: 3.1.0
       ember-source: 5.0.0(@babel/core@7.23.2)(@glimmer/component@1.1.2)(webpack@5.86.0)
       qunit: 2.20.0
+      qunit-theme-ember: 1.0.0
     transitivePeerDependencies:
       - '@glint/template'
       - supports-color
diff --git a/test-buildtime-options-app/ember-cli-build.js b/test-buildtime-options-app/ember-cli-build.js
index f5ba7f7a..b7eba20c 100644
--- a/test-buildtime-options-app/ember-cli-build.js
+++ b/test-buildtime-options-app/ember-cli-build.js
@@ -11,6 +11,7 @@ module.exports = function (defaults) {
       setConfig: {
         'ember-qunit': {
           disableContainerStyles: true,
+          theme: 'qunit-default',
         },
       },
     },
diff --git a/test-buildtime-options-app/tests/unit/theme-test.js b/test-buildtime-options-app/tests/unit/theme-test.js
new file mode 100644
index 00000000..a6b8daa3
--- /dev/null
+++ b/test-buildtime-options-app/tests/unit/theme-test.js
@@ -0,0 +1,17 @@
+import { module, test } from 'qunit';
+import { assert as debugAssert } from '@ember/debug';
+
+module('theme', function () {
+  function style(element) {
+    return window.getComputedStyle(element);
+  }
+
+  test('the qunit-default themes are present when used', async function (assert) {
+    let qunitHeader = document.getElementById('qunit-header');
+
+    debugAssert(`#qunit-header must exist`, qunitHeader);
+
+    // Defaults
+    assert.strictEqual(style(qunitHeader).backgroundColor, 'rgb(13, 51, 73)');
+  });
+});