diff --git a/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriber.kt b/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriber.kt
index 95423844c1d2c..99a0b58936cb3 100644
--- a/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriber.kt
+++ b/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriber.kt
@@ -22,6 +22,10 @@ internal class VoiceTranscriptionException(
   cause: Throwable? = null
 ) : Exception(message, cause)
 
+// ML Kit reports every mode UNAVAILABLE for tags with Unicode extensions, which Android adds
+// for regional preferences such as the temperature unit (en-US-u-mu-celsius).
+internal fun speechLocale(systemLocale: Locale): Locale = systemLocale.stripExtensions()
+
 private val recognitionModes = listOf(
   SpeechRecognizerOptions.Mode.MODE_ADVANCED,
   SpeechRecognizerOptions.Mode.MODE_BASIC
diff --git a/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/T3VoiceTranscriptionModule.kt b/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/T3VoiceTranscriptionModule.kt
index b49791bea2b9b..008406b006d18 100644
--- a/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/T3VoiceTranscriptionModule.kt
+++ b/apps/mobile/modules/t3-voice-transcription/android/src/main/java/expo/modules/t3voicetranscription/T3VoiceTranscriptionModule.kt
@@ -32,7 +32,7 @@ class T3VoiceTranscriptionModule : Module() {
       } else {
         withContext(Dispatchers.IO) {
           val context = requireNotNull(appContext.reactContext)
-          val locale = Resources.getSystem().configuration.locales[0]
+          val locale = speechLocale(Resources.getSystem().configuration.locales[0])
           isGoogleVoiceTranscriptionSupported { MlKitSpeechClient(context, locale, it) }
         }
       }
@@ -47,7 +47,7 @@ class T3VoiceTranscriptionModule : Module() {
           )
         }
         val context = requireNotNull(appContext.reactContext)
-        val locale = Resources.getSystem().configuration.locales[0]
+        val locale = speechLocale(Resources.getSystem().configuration.locales[0])
         val mode = prepareGoogleVoiceTranscription { MlKitSpeechClient(context, locale, it) }
         mapOf("locale" to locale.toLanguageTag(), "mode" to mode)
       }
diff --git a/apps/mobile/modules/t3-voice-transcription/android/src/test/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriberTest.kt b/apps/mobile/modules/t3-voice-transcription/android/src/test/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriberTest.kt
index aaa76dfbf07e2..445411bbb6957 100644
--- a/apps/mobile/modules/t3-voice-transcription/android/src/test/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriberTest.kt
+++ b/apps/mobile/modules/t3-voice-transcription/android/src/test/java/expo/modules/t3voicetranscription/GoogleVoiceTranscriberTest.kt
@@ -4,6 +4,7 @@ import com.google.mlkit.genai.common.FeatureStatus
 import com.google.mlkit.genai.common.GenAiException
 import com.google.mlkit.genai.speechrecognition.SpeechRecognizerOptions
 import com.google.mlkit.genai.speechrecognition.SpeechRecognizerResponse
+import java.util.Locale
 import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.cancelAndJoin
 import kotlinx.coroutines.flow.flow
@@ -14,6 +15,18 @@ import org.junit.Assert.assertTrue
 import org.junit.Test
 
 class GoogleVoiceTranscriberTest {
+  @Test
+  fun dropsRegionalPreferenceExtensionsFromTheSpeechLocale() {
+    for ((system, expected) in listOf(
+      "en-US-u-mu-celsius" to "en-US",
+      "en-GB-u-fw-mon-mu-celsius" to "en-GB",
+      "ar-EG-u-nu-latn" to "ar-EG",
+      "zh-Hant-TW" to "zh-Hant-TW"
+    )) {
+      assertEquals(expected, speechLocale(Locale.forLanguageTag(system)).toLanguageTag())
+    }
+  }
+
   @Test
   fun preservesUtterancesAndTheirSpacingWithoutDuplicatingHypotheses() = runBlocking {
     for ((finals, trailing, expected) in listOf(