Substance-use disorders are a public health crisis globally and carry with them significant morbidity and mortality. Stigma toward people who abuse these substances, as well as the internalization of that stigma by substance users, is widespread. In this review, we synthesized the available evidence for the role of perceived social stigma and self-stigma in people’s willingness to seek treatment. While stigma may be frequently cited as a barrier to treatment in some samples, the degree of its impact on decision-making regarding treatment varied widely. More research needs to be done to standardize the definition and measurement of self- and perceived social stigma to fully determine the magnitude of their effect on treatment-seeking decisions.