Over the past 40 years, higher education institutions in the U.S. have experienced a dramatic shiftin the racial composition of students enrolled in both undergraduate and graduate programs. Usingadministrative data from a large, diverse university in California, we identify the extent to which theacademic outcomes of undergraduates are affected by the race/ethnicity of their graduate student teaching assistants (TAs). To overcome selection issues in course taking, we exploit the timing of TA assignments, which occur after students enroll in a course, and we estimate models with both class and student fixed effects. Results show a positive and significant increase in course grades when students are assigned TAs of a similar race/ethnicity. These effects are largest in classes where TAs are given advanced copies of exams and when exams had no multiple choice questions. We also find that assignment to similar race TAs positively affect both section and office hour attendance, suggesting that TA-student match quality and role model effects are the primary drivers of the results.