diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index e6da15389..597cc9801 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -12,7 +12,7 @@ Changelog
 ------
 Fixed
 ^^^^^
-- TODO
+- Primary key field should not be nullable (#1778)
 
 Added
 ^^^^^
diff --git a/tortoise/contrib/pydantic/creator.py b/tortoise/contrib/pydantic/creator.py
index 32ff88ffd..6f2585fe5 100644
--- a/tortoise/contrib/pydantic/creator.py
+++ b/tortoise/contrib/pydantic/creator.py
@@ -513,7 +513,9 @@ def _process_data_field(
         ptype = python_type
         if field.null:
             json_schema_extra["nullable"] = True
-        if field_name in self._optional or field.default is not None or field.null:
+        if not field.pk and (
+            field_name in self._optional or field.default is not None or field.null
+        ):
             ptype = Optional[ptype]
         if not (self._exclude_read_only and json_schema_extra.get("readOnly") is True):
             return annotation or ptype