diff --git a/src/openai/_models.py b/src/openai/_models.py
index ed4c1f82d6..73457ed28d 100644
--- a/src/openai/_models.py
+++ b/src/openai/_models.py
@@ -657,7 +657,11 @@ def construct_type(*, value: object, type_: object, metadata: Optional[List[Any]
         if not is_mapping(value):
             return value
 
-        _, items_type = get_args(type_)  # Dict[_, items_type]
+        type_args = get_args(type_)  # Dict[_, items_type]
+        if len(type_args) < 2:
+            # bare `dict` with no type parameters — return the mapping as-is
+            return value
+        _, items_type = type_args
         return {key: construct_type(value=item, type_=items_type) for key, item in value.items()}
 
     if (
diff --git a/src/openai/_utils/_transform.py b/src/openai/_utils/_transform.py
index 414f38c340..ca9e980d14 100644
--- a/src/openai/_utils/_transform.py
+++ b/src/openai/_utils/_transform.py
@@ -180,8 +180,12 @@ def _transform_recursive(
         return _transform_typeddict(data, stripped_type)
 
     if origin == dict and is_mapping(data):
-        items_type = get_args(stripped_type)[1]
-        return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
+        args = get_args(stripped_type)
+        if len(args) >= 2:
+            items_type = args[1]
+            return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
+        # bare `dict` with no type parameters — return as-is
+        return data
 
     if (
         # List[T]
@@ -346,8 +350,12 @@ async def _async_transform_recursive(
         return await _async_transform_typeddict(data, stripped_type)
 
     if origin == dict and is_mapping(data):
-        items_type = get_args(stripped_type)[1]
-        return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
+        args = get_args(stripped_type)
+        if len(args) >= 2:
+            items_type = args[1]
+            return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
+        # bare `dict` with no type parameters — return as-is
+        return data
 
     if (
         # List[T]
diff --git a/tests/test_models.py b/tests/test_models.py
index cc204bac1d..4157aecab9 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -1015,3 +1015,16 @@ class Model(BaseModel):
     # falls back to list of chars rather than calling str(["h", "e", "l", "l", "o"])
     assert m.data["items"] == ["h", "e", "l", "l", "o"]
     assert m.model_dump()["data"]["items"] == ["h", "e", "l", "l", "o"]
+
+
+def test_construct_type_bare_dict_does_not_crash() -> None:
+    """construct_type must not raise ValueError when type_ is bare dict (issue #3341)."""
+    result = construct_type(value={"key": "value"}, type_=dict)
+    assert result == {"key": "value"}
+
+
+def test_construct_type_parameterised_dict_still_works() -> None:
+    """dict[str, str] must still work after the bare-dict guard."""
+    from typing import Dict
+    result = construct_type(value={"k": "v"}, type_=Dict[str, str])
+    assert result == {"k": "v"}
diff --git a/tests/test_transform.py b/tests/test_transform.py
index bece75dfc7..42ec1c7754 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -458,3 +458,25 @@ async def test_strips_notgiven(use_async: bool) -> None:
 async def test_strips_omit(use_async: bool) -> None:
     assert await transform({"foo_bar": "bar"}, Foo1, use_async) == {"fooBar": "bar"}
     assert await transform({"foo_bar": omit}, Foo1, use_async) == {}
+
+
+class TestBareDict:
+    def test_transform_bare_dict_does_not_crash(self) -> None:
+        """Bare `dict` annotation (no type args) must not raise IndexError (issues #3338 / #3341)."""
+        from typing import TypedDict
+
+        class Params(TypedDict, total=False):
+            metadata: dict  # bare, unparameterised dict
+
+        result = _transform({"metadata": {"k": "v"}}, Params)
+        assert result == {"metadata": {"k": "v"}}
+
+    def test_transform_parameterised_dict_still_works(self) -> None:
+        """dict[str, str] annotation must still recurse into values."""
+        from typing import Dict, TypedDict
+
+        class Params(TypedDict, total=False):
+            tags: Dict[str, str]
+
+        result = _transform({"tags": {"a": "b"}}, Params)
+        assert result == {"tags": {"a": "b"}}