Heterosexist discrimination is a known predictor of poorer mental health among sexual minority men (SMM), but it may not be the only social stressor influencing mental health. This study examined if intragroup marginalization within the gay community contributes to SMM's mental health after accounting for experiences of heterosexist discrimination. Study participants were 283 Australian SMM (M-age = 32.12, SD = 10.81) who completed an online survey of heterosexist discrimination and intragroup marginalization, as well as levels of depression, social anxiety, self-esteem, and outness. Intragroup marginalization was measured using a new scale assessing marginalization due to social (e.g., status), individual (e.g., physical appearance), and identity (e.g., race/ethnicity) attributes. Depression, social anxiety, and self-esteem were regressed on all other measures in three hierarchical models. Individual intragroup marginalization predicted greater depression, social anxiety, and lower self-esteem; identity intragroup marginalization predicted greater depression and social anxiety; and, unexpectedly, social intragroup marginalization predicted lower social anxiety and greater self-esteem. These associations persisted after considering heterosexist discrimination, which predicted poorer mental health outcomes, while outness was not a significant predictor. The results reveal varied associations between intragroup marginalization, heterosexist discrimination, and mental health, suggesting complex relationships between multilateral stressors and SMM's mental health.