Gender disparities in STEM persist despite girls performing as well as boys academically, suggesting girls may benefit from role models who shape their perceptions of STEM. We examine whether female math tutors influence girls’ STEM interest, attendance, and performance. We randomly assigned 422 ninth-grade students taking Algebra 1 to a same gender or opposite-gender tutor. Girls assigned to female tutors reported higher STEM interest (0.73 SD) and were more likely to pass the course with a C- or better (3.9-percentage points) than those with male tutors. We found no impact on attendance. Effects were stronger for students working with tutors in-person rather than virtually. We provide the first experimental evidence that female tutors can boost girls’ STEM self-concept and academic outcomes.