On February 18, 2015, Hosmer and the Royals agreed to a $13.9 million, two-year contract. He would earn $5.65 million during the 2015 season and $8.25 million during the 2016 season, and would be eligible for arbitration again in 2017. He would not be eligible for free agency until the 2017 Off season. During the 2015 season, Hosmer had a career year with a .297 batting average, with 18 home runs and 93 RBIs. Hosmer also recorded the final putout of the AL Central and the American League Championship Series clinching games. On October 23, Hosmer tied George Brett for the most RBIs in the postseason (23) in Royals' franchise history when he singled Lorenzo Cain home from first base representing the go-ahead run in Game 6 of the ALCS. In Game 1 of the 2015 World Series, Hosmer overtook Brett's record for the most RBIs in the postseason with a walk-off sacrifice fly to bring in Alcides Escobar in the 14th inning, representing Hosmer's 25th postseason RBI and helping atone for an eighth-inning error that helped the Mets take a one-run lead. Hosmer starred again in game 2 with two hits, a run scored, and two RBIs to help the Royals take a 7-1 win and a 2-0 series lead. On November 1, 2015 Hosmer scored the tying run in the 9th inning which eventually led to the Royals win in game 5 of the World Series