There is mixed evidence for whether or not co-occurring anxiety is associated with poorer peer functioning in children with attention-deficit/hyperactivity disorder (ADHD), which may be partly due to studies typically using a global measure of anxiety and failing to consider possible sex differences. The present study examined child-reported social anxiety in relation to peer functioning and whether this association differs by sex in 93 children (66% male; ages 8-12) with ADHD. Children, parents, and teachers completed a measure of social acceptance, and teachers also completed measures of asociality, peer exclusion, peer dislike, and peer ignoring. Regression analyses examined the interaction between social anxiety and sex in relation to the peer functioning variables, with age, race, ADHD subtype, and oppositional defiant disorder symptoms included as covariates. Social anxiety was associated with lower parent-reported social acceptance, with no sex differences in the association. However, significant interaction effects were found for child- and teacher-rated social acceptance, as well as peer exclusion and peer ignoring such that social anxiety was associated with less competence, more exclusion, and greater ignoring for girls but not boys. Findings indicate that social anxiety is associated with poorer peer functioning for girls more so than boys with ADHD.