Martinez was named to the 2023 World Baseball Classic roster.

Won a silver medal with Team USA at the Tokyo 2020 Olympic Games. Led Team USA in innings pitched with 11 after making two starts in the tournament. He also led the team with 16 strikeouts, doubling the next-highest pitcher. After giving up back-to-back singles and a run in his start over Korea in the Group B finale, Martinez sat down 13 of the next 14 batters he faced, including striking out the side in the third inning for three of his nine punch outs, helping tie the U.S. Olympic record for strikeouts in a game with 14. Got the start against Japan in the gold medal game and had a strong outing for the U.S., keeping Japan to just one run in the gold medal game. He finished with seven strikeouts and gave up five hits and one run in six innings of work in the loss.