diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 4970515cd9..47f8716114 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -11,6 +11,9 @@
         `ExoPlayer.Builder`.
     *   Fix bug where prepare errors in the content of `AdsMediaSource` may be
         never reported ([#2337](https://github.com/androidx/media/issues/2337)).
+    *   Fix memory leak in `MergingMediaSource`, for example used when
+        sideloading subtitles
+        ([#2338](https://github.com/androidx/media/issues/2338)).
 *   Transformer:
     *   Filling an initial gap (added via `addGap()`) with silent audio now
         requires explicitly setting `experimentalSetForceAudioTrack(true)` in
diff --git a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MergingMediaSource.java b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MergingMediaSource.java
index d61a5b2319..d8f136ad57 100644
--- a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MergingMediaSource.java
+++ b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MergingMediaSource.java
@@ -245,8 +245,9 @@ public final class MergingMediaSource extends CompositeMediaSource<Integer> {
     MergingMediaPeriod mergingPeriod = (MergingMediaPeriod) mediaPeriod;
     for (int i = 0; i < mediaSources.length; i++) {
       List<MediaPeriodAndId> mediaPeriodsForSource = mediaPeriods.get(i);
+      MediaPeriod childPeriod = mergingPeriod.getChildPeriod(i);
       for (int j = 0; j < mediaPeriodsForSource.size(); j++) {
-        if (mediaPeriodsForSource.get(j).mediaPeriod.equals(mediaPeriod)) {
+        if (mediaPeriodsForSource.get(j).mediaPeriod.equals(childPeriod)) {
           mediaPeriodsForSource.remove(j);
           break;
         }
diff --git a/libraries/exoplayer/src/test/java/androidx/media3/exoplayer/source/MergingMediaSourceTest.java b/libraries/exoplayer/src/test/java/androidx/media3/exoplayer/source/MergingMediaSourceTest.java
index 5630e97945..7335fa02bd 100644
--- a/libraries/exoplayer/src/test/java/androidx/media3/exoplayer/source/MergingMediaSourceTest.java
+++ b/libraries/exoplayer/src/test/java/androidx/media3/exoplayer/source/MergingMediaSourceTest.java
@@ -16,6 +16,7 @@
 package androidx.media3.exoplayer.source;
 
 import static androidx.media3.test.utils.robolectric.RobolectricUtil.DEFAULT_TIMEOUT_MS;
+import static androidx.media3.test.utils.robolectric.RobolectricUtil.runMainLooperUntil;
 import static com.google.common.truth.Truth.assertThat;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.junit.Assert.assertThrows;
@@ -24,8 +25,11 @@ import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.Timeline;
 import androidx.media3.common.util.Util;
+import androidx.media3.exoplayer.analytics.PlayerId;
 import androidx.media3.exoplayer.source.MediaSource.MediaPeriodId;
 import androidx.media3.exoplayer.source.MergingMediaSource.IllegalMergeException;
+import androidx.media3.exoplayer.upstream.Allocator;
+import androidx.media3.exoplayer.upstream.DefaultAllocator;
 import androidx.media3.test.utils.FakeMediaPeriod;
 import androidx.media3.test.utils.FakeMediaSource;
 import androidx.media3.test.utils.FakeTimeline;
@@ -36,7 +40,10 @@ import com.google.common.collect.ConcurrentHashMultiset;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Multiset;
 import java.io.IOException;
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicReference;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -219,6 +226,57 @@ public class MergingMediaSourceTest {
     }
   }
 
+  @Test
+  public void createAndReleasePeriods_cleansUpReferences() throws Exception {
+    ArrayList<WeakReference<MediaPeriod>> createdChildPeriods = new ArrayList<>();
+    FakeMediaSource childSource =
+        new FakeMediaSource() {
+          @Override
+          public MediaPeriod createPeriod(
+              MediaPeriodId id, Allocator allocator, long startPositionUs) {
+            MediaPeriod period = super.createPeriod(id, allocator, startPositionUs);
+            createdChildPeriods.add(new WeakReference<>(period));
+            return period;
+          }
+        };
+    Allocator allocator =
+        new DefaultAllocator(/* trimOnReset= */ true, /* individualAllocationSize= */ 1024);
+    MergingMediaSource mergingMediaSource =
+        new MergingMediaSource(
+            /* adjustPeriodTimeOffsets= */ true,
+            /* clipDurations= */ true,
+            childSource,
+            childSource);
+    AtomicReference<Timeline> timelineReference = new AtomicReference<>();
+    mergingMediaSource.prepareSource(
+        (source, timeline) -> timelineReference.set(timeline),
+        /* mediaTransferListener= */ null,
+        PlayerId.UNSET);
+    runMainLooperUntil(() -> timelineReference.get() != null);
+    Object periodUid = timelineReference.get().getUidOfPeriod(/* periodIndex= */ 0);
+
+    // Create 20 periods.
+    ArrayList<MediaPeriod> createdMergedPeriods = new ArrayList<>();
+    for (int i = 0; i < 20; i++) {
+      createdMergedPeriods.add(
+          mergingMediaSource.createPeriod(
+              new MediaPeriodId(periodUid, /* windowSequenceNumber= */ i),
+              allocator,
+              /* startPositionUs= */ 0));
+    }
+    // Release 19 periods.
+    for (int i = 0; i < 19; i++) {
+      mergingMediaSource.releasePeriod(createdMergedPeriods.remove(0));
+    }
+    // Ensure all pending references are garbage collected
+    Runtime.getRuntime().gc();
+
+    // Assert that only 2 child periods remain in memory.
+    long nonNullChildPeriodReferences =
+        createdChildPeriods.stream().filter(reference -> reference.get() != null).count();
+    assertThat(nonNullChildPeriodReferences).isEqualTo(2);
+  }
+
   /**
    * Wraps the specified timelines in a {@link MergingMediaSource}, prepares it and returns the
    * merged timeline.