In his Royals debut, Rios hit a 3-run home run in a Royals win to cap off a three-hit game. For the 2015 season, Rios hit .255 with 4 home runs and 32 RBIs while appearing in 105 games. While he had a down year with Kansas City, Rios had many notable moments in the 2015 MLB Playoffs. In Game 4 of the 2015 American League Division Series, Rios hit a leadoff single in the top of the eighth inning, sparking a five-run inning that erased a four-run deficit and forced a Game 5 of the series. In Game 5, Rios hit a two-RBI double in the bottom of the fifth inning, driving in what proved to be the winning runs of the game. Rios was just as pivotal in the 2015 American League Championship Series, batting .368 with a home run and three runs batted in. At the end of the season, the Kansas City Royals won the World Series, giving Rios his first championship ring.