Bring Change 2 Mind (BC2M) high school clubs may destigmatize mental illness among club members, but clubs (1) reach and impact on non-club members at the same school, (2) connection to student help-seeking attitudes, and (3) mechanisms by which they destigmatize mental illness, are unknown. This community-partnered evaluation involved pre/post surveys of predominantly Latino (72%) students at three urban public schools and focus groups and interviews with a sample of club members (n = 26/65, 40%) and all club staff (n = 7, 100%). Multivariate regressions tested relationships between variables. In 84% of the student body responded in the Fall (n = 1,040) and Spring (n = 1,031). Non-club member engagement in BC2M (reach) increased from 25% (Fall) to 44% (Spring) (p < .01). Engagement with BC2M clubs was associated with decreased stigma among members (p < .05) but not non-members (p = .19). Decreased stigma was associated with help-seeking attitudes (p < .01). Possible BC2M mechanisms identified by students and staff include the following: (1) fostering a positive campus climate, (2) normalizing mental health discussions, (3) increasing peer support and help-seeking, and (4) increasing awareness of positive coping behaviors. While BC2M clubs likely reduce stigma for members, effects did not reach non-members, challenging the potential of BC2M clubs as a schoolwide strategy to destigmatize mental health services. Future projects could investigate how to reach non-BC2M members, complement BC2M with other school climate interventions to increase impact, and measure BC2M impact alongside other outcomes relevant to schools, such as academic achievement.