Objective: Online racial discrimination (ORD) is rampant; however, little is known about its associations with mental health among undergraduates. This study explored the relations between ORD and mental health among Black undergraduates. It also investigated gender differences in these relations. Participants: Two hundred seventy-eight Black, cisgender men and women enrolled in a minority-serving public university in the Northeast U.S. Methods: Participants completed measures of ORD, depression, generalized anxiety (GA), and social anxiety (SA) via a Web-based survey. Results: Eighty-five percent of participants experienced at least one ORD incident in the last year. Men and women reported comparable exposure. Gender moderated the relations between ORD and depression and SA, respectively; these associations were stronger for women. Conclusions: Exposure to ORD is prevalent among Black undergraduates and is associated with adverse mental health outcomes, especially for women. Campus mental health interventions should address online discrimination in the context of students' intersecting identities.