on january 25, 2018, the brewers traded harrison, isan díaz, lewis brinson, and jordan yamamoto to the miami marlins for christian yelich. mlb.com ranked harrison as miami's second best prospect going into the 2018 season. he spent 2018 with the jacksonville jumbo shrimp, hitting .240 with 19 home runs, 48 rbis, and 28 stolen bases in 136 games.