diff --git a/CHANGELOG.md b/CHANGELOG.md
index c21a8cce7d..0446a766e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,10 @@
   ```
 - Parse ART memory and garbage collector info from ANR tombstones into ART context ([#5428](https://github.com/getsentry/sentry-java/pull/5428))
 
+### Improvements
+
+- Improve SDK init performance by deferring `ReplayIntegration.start()` off the main thread ([#5474](https://github.com/getsentry/sentry-java/pull/5474))
+
 ## 8.42.0
 
 ### Features
diff --git a/sentry-android-replay/src/main/java/io/sentry/android/replay/ReplayIntegration.kt b/sentry-android-replay/src/main/java/io/sentry/android/replay/ReplayIntegration.kt
index 07e91d7648..b6770d0770 100644
--- a/sentry-android-replay/src/main/java/io/sentry/android/replay/ReplayIntegration.kt
+++ b/sentry-android-replay/src/main/java/io/sentry/android/replay/ReplayIntegration.kt
@@ -161,6 +161,7 @@ public class ReplayIntegration(
     lifecycle.currentState >= STARTED && lifecycle.currentState < STOPPED
 
   override fun start() {
+    val isFullSession: Boolean
     lifecycleLock.acquire().use {
       if (!isEnabled.get()) {
         return
@@ -174,7 +175,7 @@ public class ReplayIntegration(
         return
       }
 
-      val isFullSession = random.sample(options.sessionReplay.sessionSampleRate)
+      isFullSession = random.sample(options.sessionReplay.sessionSampleRate)
       if (!isFullSession && !options.sessionReplay.isSessionReplayForErrorsEnabled) {
         options.logger.log(
           INFO,
@@ -184,30 +185,39 @@ public class ReplayIntegration(
       }
 
       lifecycle.currentState = STARTED
-      captureStrategy =
-        replayCaptureStrategyProvider?.invoke(isFullSession)
-          ?: if (isFullSession) {
-            SessionCaptureStrategy(
-              options,
-              scopes,
-              dateProvider,
-              replayExecutor,
-              replayCacheProvider,
-            )
-          } else {
-            BufferCaptureStrategy(
-              options,
-              scopes,
-              dateProvider,
-              random,
-              replayExecutor,
-              replayCacheProvider,
-            )
-          }
-      recorder?.start()
-      captureStrategy?.start()
+    }
+
+    // Defer the expensive work (strategy creation, recorder start, listener registration)
+    // off the calling thread to avoid blocking SentryAndroid.init() on the main thread.
+    options.executorService.submitSafely(options, "ReplayIntegration.start") {
+      lifecycleLock.acquire().use {
+        captureStrategy =
+          replayCaptureStrategyProvider?.invoke(isFullSession)
+            ?: if (isFullSession) {
+              SessionCaptureStrategy(
+                options,
+                scopes,
+                dateProvider,
+                replayExecutor,
+                replayCacheProvider,
+              )
+            } else {
+              BufferCaptureStrategy(
+                options,
+                scopes,
+                dateProvider,
+                random,
+                replayExecutor,
+                replayCacheProvider,
+              )
+            }
+        recorder?.start()
+        captureStrategy?.start()
+      }
 
-      registerRootViewListeners()
+      // Post to main thread since registerRootViewListeners triggers View operations
+      // (e.g. addOnLayoutChangeListener) via the OnRootViewsChangedListener callback
+      mainLooperHandler.post { registerRootViewListeners() }
     }
   }
 
diff --git a/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplayIntegrationWithRecorderTest.kt b/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplayIntegrationWithRecorderTest.kt
index 75626f4e4c..d6dcdb1ad7 100644
--- a/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplayIntegrationWithRecorderTest.kt
+++ b/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplayIntegrationWithRecorderTest.kt
@@ -18,6 +18,7 @@ import io.sentry.android.replay.ReplayIntegrationWithRecorderTest.LifecycleState
 import io.sentry.android.replay.util.ReplayShadowMediaCodec
 import io.sentry.rrweb.RRWebMetaEvent
 import io.sentry.rrweb.RRWebVideoEvent
+import io.sentry.test.ImmediateExecutorService
 import io.sentry.transport.CurrentDateProvider
 import io.sentry.transport.ICurrentDateProvider
 import io.sentry.util.thread.NoOpThreadChecker
@@ -44,7 +45,11 @@ class ReplayIntegrationWithRecorderTest {
   @get:Rule val tmpDir = TemporaryFolder()
 
   internal class Fixture {
-    val options = SentryOptions().apply { threadChecker = NoOpThreadChecker.getInstance() }
+    val options =
+      SentryOptions().apply {
+        threadChecker = NoOpThreadChecker.getInstance()
+        executorService = ImmediateExecutorService()
+      }
     val scopes = mock<IScopes>()
 
     fun getSut(
diff --git a/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplaySmokeTest.kt b/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplaySmokeTest.kt
index c26e6be9c4..b55b302033 100644
--- a/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplaySmokeTest.kt
+++ b/sentry-android-replay/src/test/java/io/sentry/android/replay/ReplaySmokeTest.kt
@@ -21,6 +21,7 @@ import io.sentry.SentryReplayEvent.ReplayType
 import io.sentry.android.replay.util.ReplayShadowMediaCodec
 import io.sentry.rrweb.RRWebMetaEvent
 import io.sentry.rrweb.RRWebVideoEvent
+import io.sentry.test.ImmediateExecutorService
 import io.sentry.transport.CurrentDateProvider
 import io.sentry.transport.ICurrentDateProvider
 import java.time.Duration
@@ -59,7 +60,7 @@ class ReplaySmokeTest {
   @get:Rule val tmpDir = TemporaryFolder()
 
   internal class Fixture {
-    val options = SentryOptions()
+    val options = SentryOptions().apply { executorService = ImmediateExecutorService() }
     val scope = Scope(options)
     val scopes =
       mock<IScopes> {