Early in the 2018 season, Moreland split time with Hanley Ramírez as Boston's first baseman, until Ramírez was designated for assignment on May 25. On July 8, Moreland was named to the 2018 MLB All-Star Game as an American League reserve first baseman. At that point in the season, Moreland had a slash line of .288/.358/.525 with 11 home runs and 43 RBIs in 71 games played. After the All Star break, Moreland struggled offensively, hitting .191 with 4 home runs in 47 games. Overall, Moreland finished hitting .245 with 15 home runs and 68 RBIs. In the postseason, Moreland appeared in 11 games, batting 5-for-17 (.294) as the Red Sox went on to win the World Series over the Los Angeles Dodgers.