On July 1, Céspedes suffered a hamstring injury while running against the Tigers on a RBI hit by Brandon Moss. Céspedes along with 5 other A's players (Josh Donaldson, Derek Norris, Brandon Moss, and pitchers Scott Kazmir and Sean Doolittle) were chosen to play in the 2014 MLB All-Star Game in Target Field. In the final week of fan voting to select starters for the All Star Game, he was passed by Adam Jones. On July 14, 2014, Céspedes won the Home Run Derby for a second time, becoming the first player to win consecutive Home Run Derby titles since Ken Griffey Jr. accomplished the feat in 1999. Céspedes played in the 2014 MLB All-Star Game where he went 0 for 2.
On July 31, 2014, Céspedes was traded to the Boston Red Sox in exchange for pitcher Jon Lester and utility player Jonny Gomes.
Céspedes hit his first home run as a member of the Red Sox on August 10, 2014, against the Los Angeles Angels, with a 3-run home run. In 51 games with Boston, Céspedes batted .269 with 5 home runs and 33 RBIs. Overall, for the 2014 season, Céspedes had 22 home runs with 100 RBIs, while batting .260.
On December 11, 2014, the Red Sox traded Céspedes along with Alex Wilson and Gabe Speier to the Detroit Tigers for Rick Porcello. Céspedes played his first game with the Tigers during opening day against the Minnesota Twins on April 6, 2015, where he robbed Kurt Suzuki of a home run, leading to a 4–0 victory for the Tigers. Through June 13, Céspedes was hitting .308 with 9 home runs and 33 runs batted in. He was not selected as an All Star but was put in as a player on the All-Star Final Vote. Therefore, he could not compete in the home run derby after winning the two previous years.
In 2014, Céspedes signed with Jay-Z's Roc Nation Sports, a sports agency division of Roc Nation. An exotic car owner, Céspedes arrived to 2016 Mets spring training with a variety of custom sports cars on display. His collection includes a custom 2016 Ford F-250, two custom Polaris Slingshots, a custom Lamborghini Aventador, an Alfa Romeo 8C Competizione, and a custom Jeep Wrangler, all totaling a little under $1 million.