Alfaro signed a minor-league contract with the Marlins on Tuesday, Jordan McPherson of the Miami Herald reports.
It's a return to South Beach for Alfaro, who played for the Marlins from 2019-21. The 30-year-old catcher has seen brief action in the majors this season with the Red Sox and Rockies but has spent most of the year at the Triple-A level. That's where he'll report this week, joining the Marlins' affiliate in Jacksonville.