diff --git a/changelog/fixed/aliased-armadillo.md b/changelog/fixed/aliased-armadillo.md
new file mode 100644
index 0000000000..685653ccba
--- /dev/null
+++ b/changelog/fixed/aliased-armadillo.md
@@ -0,0 +1 @@
+`temporalio.contrib.pydantic`: setting `ToJsonOptions` on the Pydantic payload converter no longer drops field aliases or serializes `inf`/`nan` as `null`; the JSON output now matches the default converter apart from the options themselves.
diff --git a/temporalio/contrib/pydantic.py b/temporalio/contrib/pydantic.py
index 94e4363db0..bb8fe0010a 100644
--- a/temporalio/contrib/pydantic.py
+++ b/temporalio/contrib/pydantic.py
@@ -73,7 +73,11 @@ def __init__(
         """
         if max_cached_type_adapters is not None and max_cached_type_adapters < 0:
             raise ValueError("max_cached_type_adapters cannot be negative")
-        self._schema_serializer = SchemaSerializer(any_schema())
+        # Match the defaults of pydantic_core.to_json so that the options only
+        # change what they control
+        self._schema_serializer = SchemaSerializer(
+            any_schema(), config={"ser_json_inf_nan": "constants"}
+        )
         self._to_json_options = to_json_options
         self._type_adapter: functools._lru_cache_wrapper[TypeAdapter[Any]] = (
             functools.lru_cache(maxsize=max_cached_type_adapters)(TypeAdapter)
@@ -107,7 +111,7 @@ def to_payload(self, value: Any) -> temporalio.api.common.v1.Payload | None:
         """
         data = (
             self._schema_serializer.to_json(
-                value, exclude_unset=self._to_json_options.exclude_unset
+                value, by_alias=True, exclude_unset=self._to_json_options.exclude_unset
             )
             if self._to_json_options
             else to_json(value)
diff --git a/tests/contrib/pydantic/test_pydantic.py b/tests/contrib/pydantic/test_pydantic.py
index 18570b3976..c3ab95f181 100644
--- a/tests/contrib/pydantic/test_pydantic.py
+++ b/tests/contrib/pydantic/test_pydantic.py
@@ -86,6 +86,48 @@ class Model(BaseModel):
     assert restored._type_adapter.cache_info().hits == 1
 
 
+class AliasModel(BaseModel):
+    order_id: int = pydantic.Field(default=-1, alias="orderId")
+    note: str = ""
+    ratio: float = 1.0
+    wait: datetime.timedelta = datetime.timedelta(seconds=1)
+    data: bytes = b"data"
+
+
+@pytest.mark.parametrize(
+    "value",
+    [
+        AliasModel(orderId=7),
+        float("inf"),
+        float("-inf"),
+        float("nan"),
+        [float("inf"), 1.5, float("nan")],
+        {"ratio": float("inf")},
+        {"wait": datetime.timedelta(minutes=1), "data": b"data"},
+    ],
+)
+def test_to_json_options_wire_format_matches_default(value: object):
+    default_payload = PydanticJSONPlainPayloadConverter().to_payload(value)
+    for options in (
+        temporalio.contrib.pydantic.ToJsonOptions(),
+        temporalio.contrib.pydantic.ToJsonOptions(exclude_unset=False),
+    ):
+        options_payload = PydanticJSONPlainPayloadConverter(options).to_payload(value)
+        assert default_payload is not None
+        assert options_payload is not None
+        assert options_payload.data == default_payload.data
+
+
+def test_to_json_options_exclude_unset_keeps_aliases():
+    converter = PydanticJSONPlainPayloadConverter(
+        temporalio.contrib.pydantic.ToJsonOptions(exclude_unset=True)
+    )
+    payload = converter.to_payload(AliasModel(orderId=7))
+    assert payload is not None
+    assert payload.data == b'{"orderId":7}'
+    assert converter.from_payload(payload, AliasModel) == AliasModel(orderId=7)
+
+
 async def test_pydantic_data_converter_pickle():
     restored = pickle.loads(pickle.dumps(pydantic_data_converter))
     value = {"a": 1}