Adolescents are at increased risk of mental illness and prefer to seek help from informal supports. By increasing knowledge and skills, peers may act as gatekeepers to mental health services. The aim of the current study was to assess the effects of a brief sports-based mental health literacy program to increase competencies and intentions to both provide and seek help for mental health problems among adolescent male sports participants. A cluster-randomized controlled trial was conducted with measures taken at 3 time points: baseline (2 weeks prior to intervention), immediately postintervention, and at 1-month follow-up. Adolescents were randomized to either the intervention group (n = 47) or a waitlist control group (n = 55) at a team level (n teams = 9). Participants were 102 male adolescents 12–18 years of age (M = 14.30, SD = 1.75) from a community football club in New South Wales, Australia. A 45-min Help Out a Mate (HOAM) workshop was delivered around a usual team practice session. Compared to the waitlist control, participants in the HOAM condition reported significant increases in knowledge of signs and symptoms of mental illness, intentions to provide help to a friend who may be experiencing a mental health problem, and attitudes that promote problem recognition and help-seeking. There were no between-group differences in confidence to provide help, personal help-seeking intentions, and psychological distress. The results suggest that a brief intervention can be effective at improving the mental health literacy of young men when delivered within a sports context. Lay summary: Compared to a waitlist control, the Help Out a Mate group showed improvements in mental health literacy for depression and anxiety and intentions to provide help along with sustained improvements in attitudes that promote help-seeking and reduce stigma. Personal help-seeking intentions did not change as a result of the program.