Background: Male students’ achievements in female-dominated study programs have garnered limited research attention. This study investigates the relationship between psychology students’ perceived diversity climate and their learning outcomes in a gender-mixed computer-supported collaborative learning (CSCL) course in introductory psychology. Our main hypotheses were that the diversity climate—learning outcome relationships would be stronger for male (gender minority) than for female students (gender majority). Methods: This study used data from a large sample of university first-year students at a blended learning university ( n = 1,172, 75% female) with three points of measurement in a 9-week CSCL assignment. Findings: Moderated-mediation regression analyses confirmed that students’ perceptions of the diversity climate in their CSCL group were significantly related to gains in online learning self-efficacy among male, but not female students. Furthermore, by increasing gains in self-efficacy, climate perceptions also translated into better quiz performance among male students. Contributions: This study shows that for men perceived diversity climate is a significant determinant of their individual learning outcomes. This calls for paying more attention to the minority perspectives of males in female-dominated psychological programs to better understand why this is the case.