Sexual- and gender-minority individuals experience minority stress, which is hypothesized to underlie the mental-health disparities affecting these populations. Drawing on advances in the classification of mental disorders, we argue that transdiagnostic approaches hold great promise for understanding and reducing these disparities. In contrast to traditional diagnostic approaches, which have limited construct validity and have produced a piecemeal literature, transdiagnostic approaches (a) are evidence based, (b) account for diffuse patterns of disparities and comorbidity, (c) pinpoint psychological mechanisms linking minority stress to poor mental health, (d) reduce scientific stigma, and (e) identify efficacious and efficient points of intervention for treatment of negative outcomes of minority stress.