On December 19, 2022, MacKinnon signed a one-year, 90 million yen ($) contract with the Saitama Seibu Lions of Nippon Professional Baseball (NPB). He made his NPB debut on March 31, 2023, going 1-for-4. On April 2, MacKinnon hit his first NPB home run, a solo shot off Taisuke Yamaoka of the Orix Buffaloes.
