The social work profession is grounded in social justice, and yet, social work education can perpetuate dynamics of oppression and privilege present in the larger society. As a result, students may experience microaggressions during their training. In this national survey of BSW students (N = 795), 24.9% witnessed a microaggression by a social work instructor. Students who noticed microaggressions were more likely to have experienced a microaggression themselves. They also were more likely to have a disability or identify as lesbian, gay, or bisexual. A qualitative analysis showed that most microaggressions occurred when an instructor dismissed or devalued students' backgrounds. Implications for encouraging social work students to become "upstander"s are discussed.