Although social anxiety and problematic alcohol use co-occur at alarmingly high rates, the mechanism for this co-occurrence is not well understood. The current study examined the mediating role of positive social alcohol expectancies (i.e., beliefs related to the desirable social effects of drinking) in the relationship between social anxiety and hazardous drinking (i.e., heavy drinking and negative consequences) among an ethnically and racially diverse (87% racial and/or ethnic minority) sample of undergraduate volunteers (n = 610; Mage = 19.1; 69% women). The results of structural equation modeling analyses (using AMOS 7.0) indicated that social (but not tension reduction, sexual enhancement, positive cognitive changes, or negative affective changes) alcohol outcome expectancies partially mediated the association between social anxiety and hazardous drinking; however, social anxiety had a negative direct effect on hazardous drinking. Findings implicate social alcohol outcome expectancies as a mechanism to target in treatment and prevention among socially anxious students.