On November 4, 2017, Barkett was named assistant hitting coach of the Boston Red Sox, working on the staff of new manager Alex Cora, and was in that role when the team won the 2018 World Series. He returned as Boston's assistant hitting coach for the 2019 season, and temporarily took over third base coaching duties during June, when the team's usual third base coach, Carlos Febles, had problems with his right foot. Following the 2019 Red Sox missing the playoffs, Barkett was reportedly dismissed in early October, which was confirmed by the team on October 8.