Alteration of elbow range of motion (ROM) has been observed in baseball pitchers. This study aims to compare dominant elbow ROM between early-puberty, late-puberty, and young–adult pitchers.We recruited 62 pitchers, consisting of 17 early-puberty (mean age 13.1 years old), 22 late-puberty (mean age 17.7 years old), and 23 young–adult players (mean age 19.4 years old). Dominant elbow ROMs was measured. One-way ANOVA was used to compare the differences in elbow ROM variables between 3 groups.Late-puberty pitchers exhibited a significantly lower elbow hyperextension and flexion than early-puberty or young–adult pitchers (P < .05). Valgus angle was significantly lower in young–adult (7.7°±5.5°) versus early-puberty (12.1°±2.3°) and late-puberty pitchers (13.0°±4.1°; P < .05). Young–adult pitchers had the largest forearm supination range (101.2°±18.1°), followed by early-puberty (82.5°±6.5°; P < .05) and late-puberty pitchers (70.6°±15.8°). Elbow flexion-hyperextension total range was smallest in late-puberty pitchers (130.3°±7.4°), followed by young–adult (142.6°±9.3°) and early-puberty pitchers (144.6°±8.3°; P < .05). Forearm pronation–supination total range was also smallest in late-puberty pitchers (142.0°±20.3°), followed by early-puberty (159.8°±9.5°) and young–adult pitchers (177.2°±20.8°; P < .05).These results indicate that careful monitoring of the elbow and forearm range of motion should be undertaken in adolescent baseball pitchers to prevent and or minimize injury risk.