Objective: Minority stress theory is often used as a causal explanation for substance use among lesbian, gay, and bisexual populations. This study tested whether drinking to cope with stress (DTC), loneliness, and gay community participation (GCP) mediated the relationship between one type of minority stress (i.e., internalized heterosexism, IH) and behavioral health outcomes. Method: Utilizing secondary data analysis and the PROCESS procedure, relationships between IH, the mediators (DTC, loneliness, and GCP), and outcomes (heavy drinking, alcohol problems, and psychological distress) were explored, both cross-sectionally and in a lagged manner, among both treatment seeking and non-treatment seeking problem drinking men who have sex with men (MSM). Problem drinkers (N=187) were assessed, provided brief normative feedback about their drinking, given the choice to receive brief alcohol use disorder treatment or change on their own, and then followed for 9 months. Results: Cross-sectional findings revealed that IH was significantly associated with heavy drinking, alcohol problems, and psychological distress. DTC emerged as a significant mediator of IH for all the health outcomes. Loneliness and GCP were significant mediators of IH for alcohol problems and psychological distress. Multiple mediation models reveal that all three mediators significantly contribute to IH’s effect on health outcomes. Lagged analyses did not yield any significant indirect effects. Conclusion: Findings underscore the necessity of addressing IH in psychosocial interventions along with coping skills training that emphasizes culturally relevant social support. Limitations related to generalizability and measurement are reviewed.