The Red Sox recalled Eaton from Triple-A Worcester on Monday.
Eaton will join the 26-man active roster in place of Rob Refsnyder (oblique), who was placed on the 10-day injured list. The utility player previously went 6-for-24 with three stolen bases over 14 games with the big club earlier this season. The right-handed-hitting Eaton is unlikely to see many starts versus right-handed pitching, but he could have a regular spot in the lineup versus lefties. He'll serve as Boston's designated hitter and leadoff batter in Monday's matchup with Orioles southpaw Trevor Rogers.