While the function of restricted repetitive behaviors (RRBs) in autism spectrum disorder (ASD) is unclear, RRBs may function as anxiety reduction strategies (Joosten et al. "J Autism Dev Disord" 39(3):521-531, 2009. Moreover, anxiety in ASD is associated with low social motivation (Swain et al. "J Autism Dev Disord," 2015. The present study examined social motivation as a mediator between anxiety and RRBs in a sample of 44 children (2-17 years old; 80% male) with ASD. The relationship between anxiety and IS, but not other RRBs, was partially mediated by social motivation. These findings suggest anxiety is linked to social motivation deficits in children with ASD, which may increase ritualized behaviors and difficulties with changes in routine. Implications are discussed for differing functions and treatment of RRB domains.