One pitch after ducking away from Jonathan Broxton's high-and-inside fastball, Cespedes launched a no-doubt, 433-foot drive to center field with two outs and Brock Holt on second base to give Boston back-to-back victories for the first time since a five-game winning streak from July 13-20.
Cespedes hit his 19th homer of the season and second with Boston -- one in each of the last two games. He has reached base at least once in all nine games he's played for the Red Sox since they acquired him from Oakland in a trade.
Tommy Layne (1-0) got the final out of the seventh inning for the win.
Kojo Uehara pitched the ninth for his 26th save.
Boston starter Joe Kelly opened the interleague game with seven straight balls. When he finally threw a strike to Jay Bruce, Billy Hamilton stole second and went to third on catcher Christian Vazquez's throwing error.
Kelly walked Bruce, setting up Todd Frazier's RBI single. Devin Mesoraco, who hit a grand slam and two-run homer while setting a career high with six RBIs in Cincinnati's 7-2 win over Miami on Sunday, followed with a run-scoring hit.
Latos gave up five hits and one run with one walk and five strikeouts in seven innings.
Kelly allowed five hits and two runs with three walks and four strikeouts in six innings as the Red Sox improved to 4-3 on their eight-game road trip.