Yes, you can join KiwiSaver after 65 years old. Do note that you are not eligible to receive the annual Government contribution once you are 65 years old, and your employer is not legally required to match your KiwiSaver contributions once you turn 65 (although some continue anyway). If you are over 65 years old and want to join KiwiSaver, you can apply in the same manner as anyone else over 18 years old.