Despite strong initial interest, college students-especially those from underrepresented minority (URM) backgrounds-leave STEM majors at high rates. Here, we explore the role of racial phenotypic stereotypicality, or how typical one's physical appearance is of one's racial group, in STEM persistence. In a longitudinal study, URM students were especially likely to leave STEM to the extent that they looked more stereotypical of their group; Asian American students were especially likely to leave STEM to the extent that they looked less stereotypical. Three experiments documented a possible mechanism; participants (Studies 2-4), including college advisors (Study 3), attributed greater STEM ability to more-stereotypical Asian Americans and to less-stereotypical Black women (not men), than to same-race peers. Study 4 showed that prejudice concerns, activated in interactions with Black men (not women), account for this gender difference; more-stereotypical Black men (like women) were negatively evaluated when prejudice concerns were not salient. This work has important implications for ongoing efforts to achieve diversity in STEM.