To bolster knowledge of determinants of relationship functioning among sexual minorities, the current meta-analysis aimed to quantitatively review evidence for the association between social stigma and relationship functioning as well as examine potential moderators. Thirty-five studies were identified, including 130 effect sizes (39 independent; N = 10,745). Across studies, evidence was found for a small but significant inverse association between social stigma and relationship functioning. Furthermore, this association was moderated by stigma type (with more deleterious associations for internalized relative to perceived stigma) and dimension of relationship functioning (with more deleterious associations for affective relative to cognitive and negative relative to positive). Evidence for demographic moderators (region, sex, race, age) was generally mixed although important limitations related to unique characteristics of study samples are discussed. We conclude by highlighting the importance of social stigma for relationship functioning and point toward directions for future research and policy action.