As part of the agreement announced Wednesday, Tazawa could earn a $25,000 performance bonus for pitching in 70 games. The deal is not guaranteed.
Tazawa, 29, was 2-7 with three saves and a 4.14 ERA in 61 relief appearances last year, his third straight season with 60 games or more. A right-hander, he is 14-18 with four saves and a 3.47 ERA in 249 career big league games, including four starts.
After earning $2.25 million last year, Tazawa had asked for a raise to $4.15 million in arbitration and had been offered $2.7 million. The agreement was $50,000 below the midpoint.
Left-hander Robbie Ross Jr. is Boston's last player in arbitration.