BACKGROUND: To investigate whether perceived attitudes of family and peers toward same-sex marriage (SSM) is a type of distal sexual minority stressor, as defined in minority stress theory, this cross-sectional study examined the associations of perceived attitudes of family and peers toward SSM with perceived sexual stigma from family and peers, internalized homonegativity, and mental health problems (e.g., depression, loneliness, anxiety) among gay and bisexual men in Taiwan. METHODS: We recruited 400 gay and bisexual men and assessed their perceived attitudes of family and peers toward SSM; perceived sexual stigma from family and peers; internalized homonegativity; and severity of depression, loneliness, and anxiety. RESULTS: Perceived attitudes of family and peers toward SSM (1) significantly correlated with various aspects of perceived sexual stigma from family and peers and (2) were significantly associated with internalized homonegativity, depression, loneliness, and anxiety. CONCLUSIONS: Perceived attitudes of family and peers toward SSM matched the characteristics of a distal sexual minority stressor, and as a new type of distal sexual minority stressor for lesbian, gay, and bisexual individuals, these perceived attitudes and related stress warrant greater attention from mental health professionals for the development of intervention programs.