diff --git a/src/betterproto/__init__.py b/src/betterproto/__init__.py
index cbafc838d..fe997a2ae 100644
--- a/src/betterproto/__init__.py
+++ b/src/betterproto/__init__.py
@@ -1714,7 +1714,10 @@ def to_pydict(
         defaults = self._betterproto.default_gen
         for field_name, meta in self._betterproto.meta_by_field_name.items():
             field_is_repeated = defaults[field_name] is list
-            value = getattr(self, field_name)
+            try:
+                value = getattr(self, field_name)
+            except AttributeError:
+                value = self._get_field_default(field_name)
             cased_name = casing(field_name).rstrip("_")  # type: ignore
             if meta.proto_type == TYPE_MESSAGE:
                 if isinstance(value, datetime):
@@ -1795,7 +1798,11 @@ def from_pydict(self: T, value: Mapping[str, Any]) -> T:
 
             if value[key] is not None:
                 if meta.proto_type == TYPE_MESSAGE:
-                    v = getattr(self, field_name)
+                    try:
+                        v = getattr(self, field_name)
+                    except AttributeError:
+                        v = self._get_field_default(field_name)
+                        setattr(self, field_name, v)
                     if isinstance(v, list):
                         cls = self._betterproto.cls_by_field[field_name]
                         for item in value[key]:
@@ -1811,7 +1818,11 @@ def from_pydict(self: T, value: Mapping[str, Any]) -> T:
                         # assignment here is necessary.
                         v.from_pydict(value[key])
                 elif meta.map_types and meta.map_types[1] == TYPE_MESSAGE:
-                    v = getattr(self, field_name)
+                    try:
+                        v = getattr(self, field_name)
+                    except AttributeError:
+                        v = self._get_field_default(field_name)
+                        setattr(self, field_name, v)
                     cls = self._betterproto.cls_by_field[f"{field_name}.value"]
                     for k in value[key]:
                         v[k] = cls().from_pydict(value[key][k])
diff --git a/tests/test_features.py b/tests/test_features.py
index 193e6b250..6274c51e9 100644
--- a/tests/test_features.py
+++ b/tests/test_features.py
@@ -181,6 +181,49 @@ class Foo(betterproto.Message):
     assert betterproto.which_one_of(foo2, "group2")[0] == ""
 
 
+def test_oneof_dict_pydict():
+
+    class Sub(betterproto.Enum):
+        aaa = 1
+        bbb = 2
+
+
+    @dataclass
+    class Foo(betterproto.Message):
+        bar: int = betterproto.int32_field(1, group="group1")
+        baz: str = betterproto.string_field(2, group="group1")
+        sub: Sub = betterproto.enum_field(3, group="group1")
+
+    foo1 = Foo(bar=1)
+
+    assert foo1.to_dict() == {"bar": 1}
+    assert foo1.to_pydict() == {"bar": 1}
+
+    foo2 = Foo(baz="baz")
+
+    assert foo2.to_dict() == {"baz": "baz"}
+    assert foo2.to_pydict() == {"baz": "baz"}
+
+    foo3 = Foo(sub=Sub.bbb)
+
+    # Enum fields should serialize as strings in to_dict, serialize as Enum values in to_pydict
+    assert foo3.to_dict() == {"sub": "bbb"}
+    assert foo3.to_pydict() == {"sub": Sub.bbb}
+
+    foo4 = Foo().from_dict({"bar": 1})
+    assert foo4.bar == 1
+
+    foo5 = Foo().from_pydict({"bar": 1})
+    assert foo5.bar == 1
+
+    foo6 = Foo().from_dict({"sub": "bbb"})
+    assert foo6.sub == Sub.bbb
+
+    foo7 = Foo().from_pydict({"sub": 2})
+    assert foo7.sub == Sub.bbb
+
+
+
 @pytest.mark.skipif(
     sys.version_info < (3, 10),
     reason="pattern matching is only supported in python3.10+",