Minority stress processes have been consistently linked to increased internalizing symptoms among sexual minority individuals. However, very little research has studied the impact of minority stress on the mental health of same-sex couples. The present study examined associations of actor and partner heterosexist microaggressions and internalized heterosexism with internalizing symptoms, moderated by dyadic coping, among male same-sex couples. Participants were 774 men who have sex with men (387 dyads). Results of actor-partner interdependence models showed that actor, but not partner, minority stress was positively associated with internalizing symptoms. Dyadic coping moderated the association of actor heterosexist microaggressions on internalizing symptoms such that for those who engaged in more dyadic coping, the association of heterosexist microaggressions with internalizing symptoms was weaker. Dyadic coping also moderated the association of partner internalized heterosexism on internalizing symptoms. For those who engaged in more dyadic coping, their partner's internalized heterosexism was associated with greater internalizing symptoms. Although dyadic coping may buffer the effects of minority stress on internalizing symptoms, if partners rely too heavily on one another to cope with stress, it may be detrimental to their mental health. Implications for relationship education interventions for same-sex couples are discussed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).