It is well established that anxiety can contribute to social functioning difficulties during childhood and adolescence. It is less clear which anxious youth are most likely to struggle socially, and what types of difficulties they are likely to experience, limiting the extent of identification and intervention efforts. In this study, we aim to improve specification of the linkages between youth anxiety severity and social functioning by examining several potential moderators of these associations. Specifically, we examine whether family accommodation of youth anxiety, in addition to youth age, sex, and the presence of a social anxiety disorder diagnosis, influence associations between anxiety severity and social functioning among youth with anxiety disorders. Youth (N = 158, Mage = 9.99 years, SD = 2.74) and their mothers completed diagnostic interviews and questionnaires assessing anxiety and depression symptoms, family accommodation, and a range of social functioning variables. In a series of hierarchical linear regressions, we found that youth anxiety severity was most strongly associated with social impairment at high levels of family accommodation for adolescents and for youth without social anxiety disorder (mother-report). We also found several direct effects of anxiety severity, family accommodation, and youth age, sex, and diagnosis on different facets of youth social functioning (youth- and/or mother-report). We discuss clinical implications and future research directions focused on specifying the nature of associations between youth anxiety and their social functioning.