Friendship group characteristics, motivation, and gender were investigated in relation to adolescents' science, technology, engineering, and math (STEM) career interest. The sample was comprised of 468 high school students (M = 16 years, range = 13–18) from diverse ethnic backgrounds. Participants rated their friendship group's support of STEM as well as their personal motivation in science. They separately rated the friendship group's support of English and personal motivation in English. Other predictors included friendship group characteristics (importance, gender composition) and background variables such as gender. Group support of STEM (but not English) and science motivation (but not English motivation) predicted STEM career interest. Group characteristics and participant gender moderated the effects. Findings suggest social identities and self‐concepts may shape youths' STEM career choices.