diff --git a/cpp/CMakeLists.txt b/cpp/CMakeLists.txt
index a1e3138da9e0b..5ead9e4b063cd 100644
--- a/cpp/CMakeLists.txt
+++ b/cpp/CMakeLists.txt
@@ -84,7 +84,7 @@ set(ARROW_VERSION "18.0.0-SNAPSHOT")
 string(REGEX MATCH "^[0-9]+\\.[0-9]+\\.[0-9]+" ARROW_BASE_VERSION "${ARROW_VERSION}")
 
 # if no build type is specified, default to release builds
-if(NOT DEFINED CMAKE_BUILD_TYPE)
+if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE
       Release
       CACHE STRING "Choose the type of build.")
diff --git a/cpp/examples/minimal_build/CMakeLists.txt b/cpp/examples/minimal_build/CMakeLists.txt
index b4a7cde938c87..95dad34221add 100644
--- a/cpp/examples/minimal_build/CMakeLists.txt
+++ b/cpp/examples/minimal_build/CMakeLists.txt
@@ -30,7 +30,7 @@ endif()
 # We require a C++17 compliant compiler
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
-if(NOT DEFINED CMAKE_BUILD_TYPE)
+if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE Release)
 endif()