diff --git a/CHANGES/1368.bugfix.rst b/CHANGES/1368.bugfix.rst
new file mode 100644
index 00000000..f541e016
--- /dev/null
+++ b/CHANGES/1368.bugfix.rst
@@ -0,0 +1 @@
+Fixed a situation where a :code:`CallbackData` could not be parsed without a default value.
diff --git a/aiogram/filters/callback_data.py b/aiogram/filters/callback_data.py
index 7a09dedb..17ccffbf 100644
--- a/aiogram/filters/callback_data.py
+++ b/aiogram/filters/callback_data.py
@@ -1,5 +1,8 @@
 from __future__ import annotations
 
+import sys
+import types
+import typing
 from decimal import Decimal
 from enum import Enum
 from fractions import Fraction
@@ -18,6 +21,7 @@ from uuid import UUID
 
 from magic_filter import MagicFilter
 from pydantic import BaseModel
+from pydantic.fields import FieldInfo
 
 from aiogram.filters.base import Filter
 from aiogram.types import CallbackQuery
@@ -27,6 +31,11 @@ T = TypeVar("T", bound="CallbackData")
 MAX_CALLBACK_LENGTH: int = 64
 
 
+_UNION_TYPES = {typing.Union}
+if sys.version_info >= (3, 10):  # pragma: no cover
+    _UNION_TYPES.add(types.UnionType)
+
+
 class CallbackDataException(Exception):
     pass
 
@@ -121,7 +130,7 @@ class CallbackData(BaseModel):
         payload = {}
         for k, v in zip(names, parts):  # type: str, Optional[str]
             if field := cls.model_fields.get(k):
-                if v == "" and not field.is_required():
+                if v == "" and _check_field_is_nullable(field):
                     v = None
             payload[k] = v
         return cls(**payload)
@@ -180,3 +189,19 @@ class CallbackQueryFilter(Filter):
         if self.rule is None or self.rule.resolve(callback_data):
             return {"callback_data": callback_data}
         return False
+
+
+def _check_field_is_nullable(field: FieldInfo) -> bool:
+    """
+    Check if the given field is nullable.
+
+    :param field: The FieldInfo object representing the field to check.
+    :return: True if the field is nullable, False otherwise.
+
+    """
+    if not field.is_required():
+        return True
+
+    return typing.get_origin(field.annotation) in _UNION_TYPES and type(None) in typing.get_args(
+        field.annotation
+    )
diff --git a/tests/test_filters/test_callback_data.py b/tests/test_filters/test_callback_data.py
index e8721a41..635b8e9f 100644
--- a/tests/test_filters/test_callback_data.py
+++ b/tests/test_filters/test_callback_data.py
@@ -1,7 +1,8 @@
+import sys
 from decimal import Decimal
 from enum import Enum, auto
 from fractions import Fraction
-from typing import Optional
+from typing import Optional, Union
 from uuid import UUID
 
 import pytest
@@ -147,6 +148,32 @@ class TestCallbackData:
         assert MyCallback3.unpack("test3:experiment:42") == MyCallback3(bar=42)
         assert MyCallback3.unpack("test3:spam:42") == MyCallback3(foo="spam", bar=42)
 
+    @pytest.mark.parametrize(
+        "hint",
+        [
+            Union[int, None],
+            Optional[int],
+        ],
+    )
+    def test_unpack_optional_wo_default(self, hint):
+        """Test CallbackData without default optional."""
+
+        class TgData(CallbackData, prefix="tg"):
+            chat_id: int
+            thread_id: hint
+
+        assert TgData.unpack("tg:123:") == TgData(chat_id=123, thread_id=None)
+
+    @pytest.mark.skipif(sys.version_info < (3, 10), reason="UnionType is added in Python 3.10")
+    def test_unpack_optional_wo_default_union_type(self):
+        """Test CallbackData without default optional."""
+
+        class TgData(CallbackData, prefix="tg"):
+            chat_id: int
+            thread_id: int | None
+
+        assert TgData.unpack("tg:123:") == TgData(chat_id=123, thread_id=None)
+
     def test_build_filter(self):
         filter_object = MyCallback.filter(F.foo == "test")
         assert isinstance(filter_object.rule, MagicFilter)