diff --git a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
index fa682920f9..bd7fa5efed 100644
--- a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
+++ b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
@@ -56,6 +56,7 @@ import androidx.media3.common.audio.ChannelMixingAudioProcessor;
 import androidx.media3.common.audio.ChannelMixingMatrix;
 import androidx.media3.common.audio.SonicAudioProcessor;
 import androidx.media3.common.util.BitmapLoader;
+import androidx.media3.common.util.Clock;
 import androidx.media3.common.util.Log;
 import androidx.media3.datasource.DataSourceBitmapLoader;
 import androidx.media3.effect.BitmapOverlay;
@@ -220,7 +221,8 @@ public final class TransformerActivity extends AppCompatActivity {
     Intent intent = getIntent();
     Uri inputUri = checkNotNull(intent.getData());
     try {
-      externalCacheFile = createExternalCacheFile("transformer-output.mp4");
+      externalCacheFile =
+          createExternalCacheFile("transformer-output-" + Clock.DEFAULT.elapsedRealtime() + ".mp4");
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }
diff --git a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/TransformerAndroidTestRunner.java b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/TransformerAndroidTestRunner.java
index 6451ed03a3..c77c080712 100644
--- a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/TransformerAndroidTestRunner.java
+++ b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/TransformerAndroidTestRunner.java
@@ -28,6 +28,7 @@ import android.net.Uri;
 import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.MediaItem;
+import androidx.media3.common.util.Clock;
 import androidx.media3.common.util.Log;
 import androidx.media3.common.util.NullableType;
 import androidx.media3.common.util.SystemClock;
@@ -339,7 +340,9 @@ public class TransformerAndroidTestRunner {
             .build();
 
     File outputVideoFile =
-        AndroidTestUtil.createExternalCacheFile(context, /* fileName= */ testId + "-output.mp4");
+        AndroidTestUtil.createExternalCacheFile(
+            context,
+            /* fileName= */ testId + "-" + Clock.DEFAULT.elapsedRealtime() + "-output.mp4");
     InstrumentationRegistry.getInstrumentation()
         .runOnMainSync(
             () -> {