After spending five seasons in the Rangers farm system, Kiner-Falefa made his major league debut in April 2018.

[1] He made his professional debut with the Arizona League Rangers and spent all of 2013 there, batting .322 with 11 RBIs and 12 stolen bases in 41 games.

On March 12, 2022, Texas traded Kiner-Falefa, along with pitcher Ronny Henríquez, to the Minnesota Twins for Mitch Garver.

[13] One day later, Minnesota traded Kiner-Falefa, along with Ben Rortvedt and Josh Donaldson, to the New York Yankees for Gary Sánchez and Gio Urshela.

[16] During spring training in 2023, Kiner-Falefa competed with Anthony Volpe and Oswald Peraza to be the Yankees starting shortstop.

[19] On April 13, 2023, Kiner-Falefa made his pitching debut in the ninth inning during an 11-2 loss for the Yankees against the Minnesota Twins.

[20] On June 14, during the Subway Series against the New York Mets, Kiner-Falefa stole home off pitcher Brooks Raley.

[21] On June 22, Kiner-Falefa was sent out for his third career pitching appearance in the top of the ninth inning of a 10–0 blowout loss against the Seattle Mariners.

Kiner-Falefa became the first Yankee to hit a home run as a pitcher since Lindy McDaniel did so on September 28, 1972, the last season before the American League's adoption of the designated hitter rule.

[29][30][31] He is the second cousin twice removed of Major League Baseball Hall of Famer Ralph Kiner on his mother's side.