On October 1, Buehler started the NL West Tie-Breaker Game against the Colorado Rockies. He picked up the win, giving up only one hit and allowing no runner to advance past second base. He also got his first career MLB run batted in in his 47th plate appearance. In 24 appearances for the Dodgers (23 starts and one relief appearance) in 2018, Buehler was 8–5 with a 2.62 ERA and 151 strikeouts. In the 2018 NLDS against the Atlanta Braves, he started one game and allowed five runs in five innings; in the 2018 NLCS against the Milwaukee Brewers he started two games, allowing five runs in innings; and he threw seven scoreless innings in Game 3 of the 2018 World Series against the Boston Red Sox. Buehler finished third in voting for the National League Rookie of the Year, behind Atlanta Braves outfielder Ronald Acuña Jr. and Washington Nationals outfielder Juan Soto.