diff --git a/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java b/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
index 572781309b..01fc9a0beb 100644
--- a/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
+++ b/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
@@ -415,7 +415,12 @@ import java.util.Locale;
    * <p>This box contains a list of metadata keys.
    */
   public static ByteBuffer keys(List<MdtaMetadataEntry> mdtaMetadataEntries) {
-    ByteBuffer contents = ByteBuffer.allocate(MAX_FIXED_LEAF_BOX_SIZE);
+    int totalSizeToStoreKeys = 0;
+    for (int i = 0; i < mdtaMetadataEntries.size(); i++) {
+      // Add header size to wrap each key into a "mdta" box.
+      totalSizeToStoreKeys += mdtaMetadataEntries.get(i).key.length() + BOX_HEADER_SIZE;
+    }
+    ByteBuffer contents = ByteBuffer.allocate(2 * BYTES_PER_INTEGER + totalSizeToStoreKeys);
     contents.putInt(0x0); // version and flags
     contents.putInt(mdtaMetadataEntries.size()); // Entry count
 
@@ -434,7 +439,15 @@ import java.util.Locale;
    * <p>This box contains a list of metadata values.
    */
   public static ByteBuffer ilst(List<MdtaMetadataEntry> mdtaMetadataEntries) {
-    ByteBuffer contents = ByteBuffer.allocate(MAX_FIXED_LEAF_BOX_SIZE);
+    int totalSizeToStoreValues = 0;
+    for (int i = 0; i < mdtaMetadataEntries.size(); i++) {
+      // Add additional 16 bytes for writing metadata associated to each value.
+      // Add header size to wrap each value into a "data" box.
+      totalSizeToStoreValues +=
+          mdtaMetadataEntries.get(i).value.length + 4 * BYTES_PER_INTEGER + BOX_HEADER_SIZE;
+    }
+
+    ByteBuffer contents = ByteBuffer.allocate(totalSizeToStoreValues);
 
     for (int i = 0; i < mdtaMetadataEntries.size(); i++) {
       int keyId = i + 1;
@@ -448,7 +461,7 @@ import java.util.Locale;
 
       valueContents.flip();
       ByteBuffer valueBox = BoxUtils.wrapIntoBox("data", valueContents);
-      contents.putInt(valueBox.remaining() + 8);
+      contents.putInt(valueBox.remaining() + BOX_HEADER_SIZE);
       contents.putInt(keyId);
       contents.put(valueBox);
     }
diff --git a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
index e71cf8bfac..1419c892f3 100644
--- a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
+++ b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
@@ -20,6 +20,7 @@ import static androidx.media3.container.MdtaMetadataEntry.TYPE_INDICATOR_FLOAT32
 import static androidx.media3.container.MdtaMetadataEntry.TYPE_INDICATOR_STRING;
 import static androidx.media3.muxer.MuxerTestUtil.FAKE_VIDEO_FORMAT;
 import static androidx.media3.muxer.MuxerTestUtil.XMP_SAMPLE_DATA;
+import static com.google.common.truth.Truth.assertThat;
 
 import android.content.Context;
 import android.media.MediaCodec.BufferInfo;
@@ -277,6 +278,27 @@ public class Mp4MuxerMetadataTest {
         MuxerTestUtil.getExpectedDumpFilePath("mp4_with_string_metadata.mp4"));
   }
 
+  @Test
+  public void writeMp4File_addManyLargeStringMetadata_doesNotThrow() throws Exception {
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
+
+    String metadataKey = "SomeStringKey";
+    byte[] metadataValue = Util.getUtf8Bytes("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    for (int i = 0; i < 100; i++) {
+      muxer.addMetadataEntry(
+          new MdtaMetadataEntry(metadataKey, metadataValue, TYPE_INDICATOR_STRING));
+    }
+    TrackToken token = muxer.addTrack(FAKE_VIDEO_FORMAT);
+
+    try {
+      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      assertThat(sampleAndSampleInfo.first.remaining()).isEqualTo(0);
+    } finally {
+      muxer.close();
+    }
+  }
+
   @Test
   public void writeMp4File_addFloatMetadata_matchesExpected() throws Exception {
     String outputFilePath = temporaryFolder.newFile().getPath();