diff --git a/src/agents/voice/__init__.py b/src/agents/voice/__init__.py
index e11ee4467f..749c6c5ed0 100644
--- a/src/agents/voice/__init__.py
+++ b/src/agents/voice/__init__.py
@@ -5,6 +5,7 @@
     StreamedTranscriptionSession,
     STTModel,
     STTModelSettings,
+    TTSCustomVoice,
     TTSModel,
     TTSModelSettings,
     TTSVoice,
@@ -29,6 +30,7 @@
     "StreamedAudioInput",
     "STTModel",
     "STTModelSettings",
+    "TTSCustomVoice",
     "TTSModel",
     "TTSModelSettings",
     "TTSVoice",
diff --git a/src/agents/voice/model.py b/src/agents/voice/model.py
index 5698fbeefe..8ed3c5b62f 100644
--- a/src/agents/voice/model.py
+++ b/src/agents/voice/model.py
@@ -5,6 +5,8 @@
 from dataclasses import dataclass
 from typing import Any, Literal
 
+from typing_extensions import TypedDict
+
 from .imports import np, npt
 from .input import AudioInput, StreamedAudioInput
 from .utils import get_sentence_based_splitter
@@ -14,22 +16,33 @@
 )
 DEFAULT_TTS_BUFFER_SIZE = 120
 
-TTSVoice = Literal[
-    "alloy",
-    "ash",
-    "ballad",
-    "coral",
-    "echo",
-    "fable",
-    "onyx",
-    "nova",
-    "sage",
-    "shimmer",
-    "verse",
-    "marin",
-    "cedar",
-]
-"""Exportable type for the TTSModelSettings voice enum"""
+
+class TTSCustomVoice(TypedDict):
+    """A custom OpenAI TTS voice reference."""
+
+    id: str
+    """The custom voice ID."""
+
+
+TTSVoice = (
+    Literal[
+        "alloy",
+        "ash",
+        "ballad",
+        "coral",
+        "echo",
+        "fable",
+        "onyx",
+        "nova",
+        "sage",
+        "shimmer",
+        "verse",
+        "marin",
+        "cedar",
+    ]
+    | TTSCustomVoice
+)
+"""Exportable type for built-in TTS voices and custom voice IDs."""
 
 
 @dataclass
diff --git a/tests/voice/test_tts_voice_types.py b/tests/voice/test_tts_voice_types.py
index 346f73132f..8cb919a159 100644
--- a/tests/voice/test_tts_voice_types.py
+++ b/tests/voice/test_tts_voice_types.py
@@ -1,7 +1,25 @@
-from typing import get_args
+from typing import Literal, get_args, get_origin
 
-from agents.voice.model import TTSVoice
+import agents.voice as voice
+from agents.voice import TTSCustomVoice, TTSModelSettings, TTSVoice
+
+
+def _builtin_voice_values() -> set[str]:
+    literal_type = next(arg for arg in get_args(TTSVoice) if get_origin(arg) is Literal)
+    return set(get_args(literal_type))
 
 
 def test_tts_voice_type_includes_current_openai_builtin_voices() -> None:
-    assert {"ballad", "verse", "marin", "cedar"} <= set(get_args(TTSVoice))
+    assert {"ballad", "verse", "marin", "cedar"} <= _builtin_voice_values()
+
+
+def test_tts_voice_type_accepts_custom_voice_ids() -> None:
+    custom_voice: TTSCustomVoice = {"id": "voice_1234"}
+    settings = TTSModelSettings(voice=custom_voice)
+
+    assert TTSCustomVoice in get_args(TTSVoice)
+    assert settings.voice == {"id": "voice_1234"}
+
+
+def test_tts_custom_voice_is_exported_from_agents_voice() -> None:
+    assert "TTSCustomVoice" in voice.__all__