diff --git a/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/manifest/DashManifestParser.java b/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/manifest/DashManifestParser.java
index 216ecc1422..45f2b6fcfc 100644
--- a/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/manifest/DashManifestParser.java
+++ b/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/manifest/DashManifestParser.java
@@ -1477,6 +1477,8 @@ public class DashManifestParser extends DefaultHandler
       case "main":
         return C.SELECTION_FLAG_DEFAULT;
       case "forced_subtitle":
+        // Support both hyphen and underscore (https://github.com/google/ExoPlayer/issues/9727).
+      case "forced-subtitle":
         return C.SELECTION_FLAG_FORCED;
       default:
         return 0;
@@ -1547,6 +1549,8 @@ public class DashManifestParser extends DefaultHandler
       case "caption":
         return C.ROLE_FLAG_CAPTION;
       case "forced_subtitle":
+        // Support both hyphen and underscore (https://github.com/google/ExoPlayer/issues/9727).
+      case "forced-subtitle":
       case "subtitle":
         return C.ROLE_FLAG_SUBTITLE;
       case "sign":
diff --git a/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/manifest/DashManifestParserTest.java b/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/manifest/DashManifestParserTest.java
index 13e5fc7e01..d446ed0f7e 100644
--- a/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/manifest/DashManifestParserTest.java
+++ b/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/manifest/DashManifestParserTest.java
@@ -254,7 +254,13 @@ public class DashManifestParserTest {
     assertThat(format.selectionFlags).isEqualTo(C.SELECTION_FLAG_FORCED);
     assertThat(adaptationSets.get(1).type).isEqualTo(C.TRACK_TYPE_TEXT);
 
+    // Ensure that forced-subtitle and forced_subtitle are both parsed as a 'forced' text track.
+    // https://github.com/google/ExoPlayer/issues/9727
     format = adaptationSets.get(2).representations.get(0).format;
+    assertThat(format.roleFlags).isEqualTo(C.ROLE_FLAG_SUBTITLE);
+    assertThat(format.selectionFlags).isEqualTo(C.SELECTION_FLAG_FORCED);
+
+    format = adaptationSets.get(3).representations.get(0).format;
     assertThat(format.containerMimeType).isEqualTo(MimeTypes.APPLICATION_TTML);
     assertThat(format.sampleMimeType).isEqualTo(MimeTypes.APPLICATION_TTML);
     assertThat(format.codecs).isNull();
@@ -586,10 +592,11 @@ public class DashManifestParserTest {
 
     assertThat(manifest.getPeriodCount()).isEqualTo(1);
     List<AdaptationSet> adaptationSets = manifest.getPeriod(0).adaptationSets;
-    assertThat(adaptationSets).hasSize(3);
+    assertThat(adaptationSets).hasSize(4);
     assertThat(getAvailabilityTimeOffsetUs(adaptationSets.get(0))).isEqualTo(C.TIME_UNSET);
     assertThat(getAvailabilityTimeOffsetUs(adaptationSets.get(1))).isEqualTo(C.TIME_UNSET);
     assertThat(getAvailabilityTimeOffsetUs(adaptationSets.get(2))).isEqualTo(C.TIME_UNSET);
+    assertThat(getAvailabilityTimeOffsetUs(adaptationSets.get(3))).isEqualTo(C.TIME_UNSET);
   }
 
   @Test
diff --git a/libraries/test_data/src/test/assets/media/mpd/sample_mpd_text b/libraries/test_data/src/test/assets/media/mpd/sample_mpd_text
index f940527037..4220f5b2f2 100644
--- a/libraries/test_data/src/test/assets/media/mpd/sample_mpd_text
+++ b/libraries/test_data/src/test/assets/media/mpd/sample_mpd_text
@@ -13,11 +13,17 @@
    </Representation>
   </AdaptationSet>
   <AdaptationSet id="0" mimeType="application/mp4" subsegmentAlignment="true">
-   <Role schemeIdUri="urn:mpeg:DASH:role:2011" value="forced_subtitle"/>
+   <Role schemeIdUri="urn:mpeg:DASH:role:2011" value="forced-subtitle"/>
    <Representation id="0" codecs="stpp.ttml.im1t" bandwidth="16">
     <BaseURL>https://test.com/0</BaseURL>
    </Representation>
   </AdaptationSet>
+  <AdaptationSet id="0" mimeType="application/mp4" subsegmentAlignment="true">
+     <Role schemeIdUri="urn:mpeg:DASH:role:2011" value="forced_subtitle"/>
+     <Representation id="0" codecs="stpp.ttml.im1t" bandwidth="16">
+      <BaseURL>https://test.com/0</BaseURL>
+     </Representation>
+    </AdaptationSet>
   <AdaptationSet id="0" mimeType="application/ttml+xml" subsegmentAlignment="true">
    <Representation id="0" bandwidth="16">
     <BaseURL>https://test.com/0</BaseURL>