diff --git a/cpp/cmake_modules/ThirdpartyToolchain.cmake b/cpp/cmake_modules/ThirdpartyToolchain.cmake
index df937cc14cb..fa8221b4a04 100644
--- a/cpp/cmake_modules/ThirdpartyToolchain.cmake
+++ b/cpp/cmake_modules/ThirdpartyToolchain.cmake
@@ -2343,13 +2343,6 @@ if(ARROW_MIMALLOC)
     set(MIMALLOC_C_FLAGS "${MIMALLOC_C_FLAGS} -DERROR_COMMITMENT_MINIMUM=635")
   endif()
 
-  set(MIMALLOC_PATCH_COMMAND "")
-  if(${UPPERCASE_BUILD_TYPE} STREQUAL "DEBUG")
-    find_program(PATCH patch REQUIRED)
-    set(MIMALLOC_PATCH_COMMAND ${PATCH} -p1 -i
-                               ${CMAKE_CURRENT_LIST_DIR}/mimalloc-1138.patch)
-  endif()
-
   set(MIMALLOC_CMAKE_ARGS
       ${EP_COMMON_CMAKE_ARGS}
       "-DCMAKE_C_FLAGS=${MIMALLOC_C_FLAGS}"
@@ -2367,7 +2360,6 @@ if(ARROW_MIMALLOC)
                       ${EP_COMMON_OPTIONS}
                       URL ${MIMALLOC_SOURCE_URL}
                       URL_HASH "SHA256=${ARROW_MIMALLOC_BUILD_SHA256_CHECKSUM}"
-                      PATCH_COMMAND ${MIMALLOC_PATCH_COMMAND}
                       CMAKE_ARGS ${MIMALLOC_CMAKE_ARGS}
                       BUILD_BYPRODUCTS "${MIMALLOC_STATIC_LIB}")
 
diff --git a/cpp/cmake_modules/mimalloc-1138.patch b/cpp/cmake_modules/mimalloc-1138.patch
deleted file mode 100644
index 1ffa4bffbba..00000000000
--- a/cpp/cmake_modules/mimalloc-1138.patch
+++ /dev/null
@@ -1,33 +0,0 @@
-# Licensed to the Apache Software Foundation (ASF) under one
-# or more contributor license agreements.  See the NOTICE file
-# distributed with this work for additional information
-# regarding copyright ownership.  The ASF licenses this file
-# to you under the Apache License, Version 2.0 (the
-# "License"); you may not use this file except in compliance
-# with the License.  You may obtain a copy of the License at
-#
-#   http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing,
-# software distributed under the License is distributed on an
-# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
-# KIND, either express or implied.  See the License for the
-# specific language governing permissions and limitations
-# under the License.
-
-Fix for https://github.com/microsoft/mimalloc/issues/1138
-
-diff --git a/src/arena.c b/src/arena.c
-index b26f4442..d7e99b55 100644
---- a/src/arena.c
-+++ b/src/arena.c
-@@ -797,6 +797,9 @@ mi_page_t* _mi_arenas_page_alloc(mi_heap_t* heap, size_t block_size, size_t bloc
-   else {
-     page = mi_arenas_page_singleton_alloc(heap, block_size, block_alignment);
-   }
-+  if mi_unlikely(page == NULL) {
-+    return NULL;
-+  }
-   // mi_assert_internal(page == NULL || _mi_page_segment(page)->subproc == tld->subproc);
-   mi_assert_internal(_mi_is_aligned(page, MI_PAGE_ALIGN));
-   mi_assert_internal(_mi_ptr_page(page)==page);