In 1921, Heilmann appeared in 149 games, including 145 as the Tigers' starting right fielder. He won his first batting title, compiling a .394 batting average to outpace his manager and teammate Ty Cobb who hit .389. Unofficial figures released in October showed Cobb as the batting champion, but official figures released in December showed Heilmann to be the champion. He was the first right-handed batter to win the American League batting title since Nap Lajoie in 1905. Heilmann also led the American League in 1921 with 237 hits and ranked second behind Babe Ruth with 139 RBIs, 365 total bases, a .606 slugging percentage, 292 times on base, a 7.3 offensive wins above replacement (WAR) rating, and 159 runs created. He also ranked among the league leaders with a .444 on-base percentage (third behind Ruth and Cobb), 43 doubles (third behind Tris Speaker and Ruth), and 76 extra base hits (third behind Ruth and Bob Meusel).