diff --git a/pandas/core/strings/accessor.py b/pandas/core/strings/accessor.py
index c2b2454c1b858..028b88cb0b1d8 100644
--- a/pandas/core/strings/accessor.py
+++ b/pandas/core/strings/accessor.py
@@ -1,12 +1,12 @@
 from __future__ import annotations
 
 import codecs
+from collections.abc import Callable  # noqa: PDF001
 from functools import wraps
 import re
 from typing import (
     TYPE_CHECKING,
     Hashable,
-    Pattern,
 )
 import warnings
 
@@ -1217,7 +1217,15 @@ def fullmatch(self, pat, case=True, flags=0, na=None):
         return self._wrap_result(result, fill_value=na, returns_string=False)
 
     @forbid_nonstring_types(["bytes"])
-    def replace(self, pat, repl, n=-1, case=None, flags=0, regex=None):
+    def replace(
+        self,
+        pat: str | re.Pattern,
+        repl: str | Callable,
+        n: int = -1,
+        case: bool | None = None,
+        flags: int = 0,
+        regex: bool | None = None,
+    ):
         r"""
         Replace each occurrence of pattern/regex in the Series/Index.
 
@@ -1358,14 +1366,10 @@ def replace(self, pat, repl, n=-1, case=None, flags=0, regex=None):
 
         is_compiled_re = is_re(pat)
         if regex:
-            if is_compiled_re:
-                if (case is not None) or (flags != 0):
-                    raise ValueError(
-                        "case and flags cannot be set when pat is a compiled regex"
-                    )
-            elif case is None:
-                # not a compiled regex, set default case
-                case = True
+            if is_compiled_re and (case is not None or flags != 0):
+                raise ValueError(
+                    "case and flags cannot be set when pat is a compiled regex"
+                )
 
         elif is_compiled_re:
             raise ValueError(
@@ -1374,6 +1378,9 @@ def replace(self, pat, repl, n=-1, case=None, flags=0, regex=None):
         elif callable(repl):
             raise ValueError("Cannot use a callable replacement when regex=False")
 
+        if case is None:
+            case = True
+
         result = self._data.array._str_replace(
             pat, repl, n=n, case=case, flags=flags, regex=regex
         )
@@ -3044,14 +3051,14 @@ def _result_dtype(arr):
         return object
 
 
-def _get_single_group_name(regex: Pattern) -> Hashable:
+def _get_single_group_name(regex: re.Pattern) -> Hashable:
     if regex.groupindex:
         return next(iter(regex.groupindex))
     else:
         return None
 
 
-def _get_group_names(regex: Pattern) -> list[Hashable]:
+def _get_group_names(regex: re.Pattern) -> list[Hashable]:
     """
     Get named groups from compiled regex.
 
diff --git a/pandas/core/strings/base.py b/pandas/core/strings/base.py
index add156efc0263..730870b448cb2 100644
--- a/pandas/core/strings/base.py
+++ b/pandas/core/strings/base.py
@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 import abc
-from typing import Pattern
+from collections.abc import Callable  # noqa: PDF001
+import re
 
 import numpy as np
 
@@ -51,7 +52,15 @@ def _str_endswith(self, pat, na=None):
         pass
 
     @abc.abstractmethod
-    def _str_replace(self, pat, repl, n=-1, case=None, flags=0, regex=True):
+    def _str_replace(
+        self,
+        pat: str | re.Pattern,
+        repl: str | Callable,
+        n: int = -1,
+        case: bool = True,
+        flags: int = 0,
+        regex: bool = True,
+    ):
         pass
 
     @abc.abstractmethod
@@ -67,7 +76,7 @@ def _str_match(
     @abc.abstractmethod
     def _str_fullmatch(
         self,
-        pat: str | Pattern,
+        pat: str | re.Pattern,
         case: bool = True,
         flags: int = 0,
         na: Scalar = np.nan,
diff --git a/pandas/core/strings/object_array.py b/pandas/core/strings/object_array.py
index 401e0217d5adf..fb9fd77d21732 100644
--- a/pandas/core/strings/object_array.py
+++ b/pandas/core/strings/object_array.py
@@ -1,8 +1,8 @@
 from __future__ import annotations
 
+from collections.abc import Callable  # noqa: PDF001
 import re
 import textwrap
-from typing import Pattern
 import unicodedata
 
 import numpy as np
@@ -15,10 +15,7 @@
     Scalar,
 )
 
-from pandas.core.dtypes.common import (
-    is_re,
-    is_scalar,
-)
+from pandas.core.dtypes.common import is_scalar
 from pandas.core.dtypes.missing import isna
 
 from pandas.core.strings.base import BaseStringArrayMethods
@@ -135,15 +132,23 @@ def _str_endswith(self, pat, na=None):
         f = lambda x: x.endswith(pat)
         return self._str_map(f, na_value=na, dtype=np.dtype(bool))
 
-    def _str_replace(self, pat, repl, n=-1, case: bool = True, flags=0, regex=True):
-        is_compiled_re = is_re(pat)
-
+    def _str_replace(
+        self,
+        pat: str | re.Pattern,
+        repl: str | Callable,
+        n: int = -1,
+        case: bool = True,
+        flags: int = 0,
+        regex: bool = True,
+    ):
         if case is False:
             # add case flag, if provided
             flags |= re.IGNORECASE
 
-        if regex and (is_compiled_re or len(pat) > 1 or flags or callable(repl)):
-            if not is_compiled_re:
+        if regex and (
+            isinstance(pat, re.Pattern) or len(pat) > 1 or flags or callable(repl)
+        ):
+            if not isinstance(pat, re.Pattern):
                 pat = re.compile(pat, flags=flags)
 
             n = n if n >= 0 else 0
@@ -195,7 +200,7 @@ def _str_match(
 
     def _str_fullmatch(
         self,
-        pat: str | Pattern,
+        pat: str | re.Pattern,
         case: bool = True,
         flags: int = 0,
         na: Scalar = None,