Social media holds promise as a technology to facilitate social engagement, but may displace offline social activities. Adolescents with ASD are well suited to capitalize on the unique features of social media, which requires less decoding of complex social information. In this cross-sectional study, we assessed social media use, anxiety and friendship quality in 44 adolescents with ASD, and 56 clinical comparison controls. Social media use was significantly associated with high friendship quality in adolescents with ASD, which was moderated by the adolescents’ anxiety levels. No associations were founds between social media use, anxiety and friendship quality in the controls. Social media may be a way for adolescents with ASD without significant anxiety to improve the quality of their friendships.