Sexual minority college students report experiencing interpersonal heterosexism, ranging from subtle insults to blatant physical violence. Such negative experiences can complicate developmental tasks common to adolescence and emerging adulthood. Studies examining the nature of heterosexism on college campuses have focused on blatant manifestations, yet subtle forms are more prevalent. Guided by ecological theory, we investigate the microsystem (e.g., perceived social support from friends, ambient heterosexism on campus), mesosystem (e.g., interaction between social support and ambient heterosexism), and macrosystem level (e.g., knowledge of gay-straight alliances on campus) covariates of interpersonal microaggressions, avoidance behaviors, verbal threats, and physical threats. Participants consisted of 530 self-identified LGBQ college students from 37 states. Regression results suggest that at the microsystem level, ambient heterosexism was positively associated with interpersonal microaggressions, avoidance behaviors, and verbal threats. At the mesosystem level, perceptions of LGBQ student support within one's institution moderated the effects of ambient heterosexism on three types of interpersonal heterosexism. At the macrosystem level, students who reported knowing that their campus had a sexual-orientation inclusive anti-discrimination policy reported encountering fewer verbal threats. Directions for future research and implications for campus programming are discussed.