diff --git a/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java
index 19086bdb7..9465c4b4c 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoader.java
@@ -66,6 +66,7 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
   private final String mSourceURL;
   private final Context mContext;
   private final int mLoadFlags;
+  private final @Nullable Runnable mOnUnpackedCallback;
 
   /**
    * Description of what needs to be unpacked.
@@ -78,6 +79,7 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
     mSourceURL = Assertions.assertNotNull(builder.sourceURL);
     mUnpackers = builder.unpackers.toArray(new Unpacker[builder.unpackers.size()]);
     mLoadFlags = builder.loadFlags;
+    mOnUnpackedCallback = builder.callback;
   }
 
   /**
@@ -85,18 +87,24 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
    * directory and unpacks everything again.
    */
   /* package */ void prepare() {
+    boolean unpacked = false;
+
     final File lockFilePath = new File(mContext.getFilesDir(), LOCK_FILE);
     Systrace.beginSection(TRACE_TAG_REACT_JAVA_BRIDGE, "UnpackingJSBundleLoader.prepare");
     try (FileLocker lock = FileLocker.lock(lockFilePath)) {
-      prepareLocked();
+      unpacked = prepareLocked();
     } catch (IOException ioe) {
       throw new RuntimeException(ioe);
     } finally {
       Systrace.endSection(TRACE_TAG_REACT_JAVA_BRIDGE);
     }
+
+    if (unpacked && mOnUnpackedCallback != null) {
+      mOnUnpackedCallback.run();
+    }
   }
 
-  private void prepareLocked() throws IOException {
+  private boolean prepareLocked() throws IOException {
     final File dotFinishedFilePath = new File(mDirectoryPath, DOT_UNPACKED_FILE);
     boolean shouldReconstruct = !mDirectoryPath.exists() || !dotFinishedFilePath.exists();
 
@@ -106,7 +114,7 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
     }
 
     if (!shouldReconstruct) {
-      return;
+      return false;
     }
 
     boolean succeeded = false;
@@ -138,6 +146,8 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
         SysUtil.dumbDeleteRecursive(mDirectoryPath);
       }
     }
+
+    return true;
   }
 
   @Override
@@ -201,6 +211,7 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
     private @Nullable String sourceURL;
     private final ArrayList<Unpacker> unpackers;
     private int loadFlags;
+    private @Nullable Runnable callback;
 
     public Builder() {
       this.unpackers = new ArrayList<Unpacker>();
@@ -208,6 +219,7 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
       destinationPath = null;
       sourceURL = null;
       loadFlags = 0;
+      callback = null;
     }
 
     public Builder setContext(Context context) {
@@ -257,6 +269,11 @@ public class UnpackingJSBundleLoader extends JSBundleLoader {
       return this;
     }
 
+    public Builder setOnUnpackedCallback(Runnable callback) {
+      this.callback = callback;
+      return this;
+    }
+
     public UnpackingJSBundleLoader build() {
       Assertions.assertNotNull(destinationPath);
       for (int i = 0; i < unpackers.size(); ++i) {
diff --git a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java
index acbaf4808..d7145409d 100644
--- a/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java
+++ b/ReactAndroid/src/test/java/com/facebook/react/cxxbridge/UnpackingJSBundleLoaderTest.java
@@ -56,6 +56,8 @@ public class UnpackingJSBundleLoaderTest {
   private CatalystInstanceImpl mCatalystInstanceImpl;
   private UnpackingJSBundleLoader.Unpacker[] mMockUnpackers;
 
+  private Runnable mCallback;
+
   @Before
   public void setUp() throws IOException {
     mDestinationPath = folder.newFolder("destination");
@@ -75,6 +77,8 @@ public class UnpackingJSBundleLoaderTest {
     for (int i = 0; i < mMockUnpackers.length; ++i) {
       mMockUnpackers[i] = mock(UnpackingJSBundleLoader.Unpacker.class);
     }
+
+    mCallback = mock(Runnable.class);
   }
 
   private void addUnpackers() {
@@ -193,4 +197,17 @@ public class UnpackingJSBundleLoaderTest {
       assertFalse(mDestinationPath.exists());
     }
   }
+
+  @Test
+  public void testCallbackIsCalledAfterUnpack() {
+    mBuilder.setOnUnpackedCallback(mCallback).build().prepare();
+    verify(mCallback).run();
+  }
+
+  @Test
+  public void testCallbackIsNotCalledIfNothingIsUnpacked() {
+    mBuilder.build().prepare();
+    mBuilder.setOnUnpackedCallback(mCallback).build().prepare();
+    verifyNoMoreInteractions(mCallback);
+  }
 }