diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5ff6b1f542e..d1a686ad4a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@
 - Session Replay: Fix `SentryOkHttpInterceptor` hanging forever on responses whose body has no known length, such as Server-Sent Events or a gzipped response, when network details are enabled for the URL ([#6231](https://github.com/getsentry/sentry-java/pull/6231))
 - Session Replay: `SentryOkHttpInterceptor` now captures network request and response details only while Session Replay is recording or buffering ([#6486](https://github.com/getsentry/sentry-java/pull/6486))
 - Stop marking an OkHttp call span as failed when a connection attempt to one of the host's addresses fails but OkHttp connects on another ([#6472](https://github.com/getsentry/sentry-java/pull/6472))
+- Fix an ANR in `SentryAndroid.init` while the connectivity and telephony callbacks are being registered ([#6511](https://github.com/getsentry/sentry-java/pull/6511))
 
 ### Dependencies
 
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProvider.java b/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProvider.java
index 62a212e6dcc..4853605b6e8 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProvider.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProvider.java
@@ -48,6 +48,10 @@ public final class AndroidConnectionStatusProvider
   private final @NotNull CellularNetworkTechnologyProvider cellularNetworkTechnologyProvider;
   private final @Nullable Handler handler;
   private final @NotNull AutoClosableReentrantLock lock = new AutoClosableReentrantLock();
+  // Guards registering and unregistering the callbacks, so `lock` is never held across those binder
+  // calls. When both are held the order is registrationLock, then `lock`.
+  private final @NotNull AutoClosableReentrantLock registrationLock =
+      new AutoClosableReentrantLock();
   private volatile @Nullable NetworkCallback networkCallback;
 
   private static final @NotNull AutoClosableReentrantLock connectivityManagerLock =
@@ -200,7 +204,7 @@ private void ensureNetworkCallbackRegistered() {
       return; // Already registered
     }
 
-    try (final @NotNull ISentryLifecycleToken ignored = lock.acquire()) {
+    try (final @NotNull ISentryLifecycleToken ignored = registrationLock.acquire()) {
       if (networkCallback != null) {
         return;
       }
@@ -457,7 +461,8 @@ public boolean addConnectionStatusObserver(final @NotNull IConnectionStatusObser
     try (final @NotNull ISentryLifecycleToken ignored = lock.acquire()) {
       connectionStatusObservers.add(observer);
     }
-    ensureNetworkCallbackRegistered();
+    //noinspection Convert2MethodRef
+    submitSafe(() -> ensureNetworkCallbackRegistered());
 
     // Network callback is already registered during initialization
     return networkCallback != null;
@@ -472,11 +477,7 @@ public void removeConnectionStatusObserver(final @NotNull IConnectionStatusObser
   }
 
   private void unregisterNetworkCallback(final boolean clearObservers) {
-    try (final @NotNull ISentryLifecycleToken ignored = lock.acquire()) {
-      if (clearObservers) {
-        connectionStatusObservers.clear();
-      }
-
+    try (final @NotNull ISentryLifecycleToken ignored = registrationLock.acquire()) {
       final @Nullable NetworkCallback callbackRef = networkCallback;
       networkCallback = null;
 
@@ -484,10 +485,16 @@ private void unregisterNetworkCallback(final boolean clearObservers) {
         unregisterNetworkCallback(context, options.getLogger(), callbackRef);
       }
       cellularNetworkTechnologyProvider.unregister();
-      // Clear cached state
-      cachedNetworkCapabilities = null;
-      currentNetwork = null;
-      cacheFreshUntil = Deadline.passed(ticker);
+
+      try (final @NotNull ISentryLifecycleToken ignored2 = lock.acquire()) {
+        if (clearObservers) {
+          connectionStatusObservers.clear();
+        }
+        // Clear cached state
+        cachedNetworkCapabilities = null;
+        currentNetwork = null;
+        cacheFreshUntil = Deadline.passed(ticker);
+      }
     }
     options.getLogger().log(SentryLevel.DEBUG, "Network callback unregistered");
   }
diff --git a/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProviderTest.kt b/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProviderTest.kt
index 56a2a12928c..84652bef351 100644
--- a/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProviderTest.kt
+++ b/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidConnectionStatusProviderTest.kt
@@ -26,9 +26,11 @@ import io.sentry.android.core.AppState
 import io.sentry.android.core.BuildInfoProvider
 import io.sentry.android.core.ContextUtils
 import io.sentry.android.core.SystemEventsBreadcrumbsIntegration
+import io.sentry.test.DeferredExecutorService
 import io.sentry.test.ImmediateExecutorService
 import io.sentry.time.TestMonotonicTicker
 import java.util.concurrent.TimeUnit.MINUTES
+import kotlin.concurrent.thread
 import kotlin.test.AfterTest
 import kotlin.test.BeforeTest
 import kotlin.test.Test
@@ -45,6 +47,7 @@ import org.mockito.kotlin.anyOrNull
 import org.mockito.kotlin.argThat
 import org.mockito.kotlin.argumentCaptor
 import org.mockito.kotlin.clearInvocations
+import org.mockito.kotlin.doAnswer
 import org.mockito.kotlin.eq
 import org.mockito.kotlin.mock
 import org.mockito.kotlin.mockingDetails
@@ -275,6 +278,39 @@ class AndroidConnectionStatusProviderTest {
     provider.close()
   }
 
+  @Test
+  @Config(sdk = [Build.VERSION_CODES.S])
+  fun `Adding an observer does not wait for the callbacks to be registered`() {
+    val telephonyManager = mock<TelephonyManager>()
+    whenever(contextMock.getSystemService(eq(Context.TELEPHONY_SERVICE)))
+      .thenReturn(telephonyManager)
+    whenever(buildInfo.sdkInfoVersion).thenReturn(Build.VERSION_CODES.S)
+    val executor = DeferredExecutorService()
+    options.executorService = executor
+    val provider = AndroidConnectionStatusProvider(contextMock, options, buildInfo, ticker)
+
+    // Both registrations are binder calls, so another thread adding an observer while either of
+    // them is running must not wait for it.
+    val observersAdded = mutableListOf<Boolean>()
+    val addObserverFromOtherThread = {
+      val other = thread { provider.addConnectionStatusObserver {} }
+      other.join(5000)
+      observersAdded.add(!other.isAlive)
+    }
+    doAnswer { addObserverFromOtherThread() }
+      .whenever(connectivityManager)
+      .registerDefaultNetworkCallback(any())
+    doAnswer { addObserverFromOtherThread() }
+      .whenever(telephonyManager)
+      .registerTelephonyCallback(any(), any())
+
+    executor.runAll()
+
+    assertEquals(listOf(true, true), observersAdded)
+    options.executorService = ImmediateExecutorService()
+    provider.close()
+  }
+
   @Test
   fun `When on cellular with a known technology, the effective type is the generation`() {
     whenever(networkCapabilities.hasTransport(eq(TRANSPORT_WIFI))).thenReturn(false)