Coping strategies have been shown to significantly influence mental and physical health among heterosexual and medically ill populations. These associations have not been thoroughly examined among sexual minority women, who are known to shoulder a high burden of disease. This study assesses the impact of adaptive and maladaptive coping on mental and physical health among 1,381 lesbian and bisexual women and examines the potential mediating role of maladaptive coping in explaining bisexual women’s poorer health relative to lesbians. Participants completed a web-based survey that assessed demographic characteristics, social support, adaptive and maladaptive coping strategies, and mental and physical health. Maladaptive coping strategies, especially behavioral disengagement and self-blame, were significantly associated with mental and physical health. Coping was more strongly predictive of mental health than physical health, and maladaptive coping more strongly predictive of health outcomes than demographics, social support, and adaptive coping. Interactions between social support and coping were generally not significant. Additionally, bisexual women reported more adverse mental and physical health outcomes than lesbians, and maladaptive coping significantly mediated these relationships. Providers working with sexual minority women may wish to pay particular attention to maladaptive coping strategies, countering these with adaptive, empowerment-based interventions.