diff --git a/cpp/cmake_modules/ThirdpartyToolchain.cmake b/cpp/cmake_modules/ThirdpartyToolchain.cmake
index 6d6a2bf7751ee..e2a75ffddbfa2 100644
--- a/cpp/cmake_modules/ThirdpartyToolchain.cmake
+++ b/cpp/cmake_modules/ThirdpartyToolchain.cmake
@@ -921,11 +921,15 @@ set(EP_COMMON_TOOLCHAIN "-DCMAKE_C_COMPILER=${EP_C_COMPILER}"
                         "-DCMAKE_CXX_COMPILER=${EP_CXX_COMPILER}")
 
 if(CMAKE_AR)
-  list(APPEND EP_COMMON_TOOLCHAIN -DCMAKE_AR=${CMAKE_AR})
+  # Ensure using absolute path.
+  find_program(EP_CMAKE_AR ${CMAKE_AR} REQUIRED)
+  list(APPEND EP_COMMON_TOOLCHAIN -DCMAKE_AR=${EP_CMAKE_AR})
 endif()
 
 if(CMAKE_RANLIB)
-  list(APPEND EP_COMMON_TOOLCHAIN -DCMAKE_RANLIB=${CMAKE_RANLIB})
+  # Ensure using absolute path.
+  find_program(EP_CMAKE_RANLIB ${CMAKE_RANLIB} REQUIRED)
+  list(APPEND EP_COMMON_TOOLCHAIN -DCMAKE_RANLIB=${EP_CMAKE_RANLIB})
 endif()
 
 # External projects are still able to override the following declarations.