Research suggests a relationship between anorexia nervosa and autism spectrum disorder. The aim of the current study was to examine social attention in anorexia nervosa and autism spectrum disorder compared with age- and sex-matched typically developing groups, and to examine whether lowered social motivation could explain reductions in social attention across the two disorders. Participants' eye movements were tracked while watching a dynamic social scene. The proportion of fixation duration to faces, bodies and non-social areas of interest were compared across groups. Participants with autism spectrum disorder looked at faces significantly less often than controls, however, there were no differences between anorexia nervosa and controls in attention to faces. Typically developing -normed z-scores indicated that attention to faces showed the greatest deviation from normative data compared with body or non-social areas of interest in both autism spectrum disorder and anorexia nervosa, however, differences were larger in autism spectrum disorder than in anorexia nervosa. Social motivation scores did not predict attention to faces in either autism spectrum disorder or anorexia nervosa. Our results do not support the hypothesis that differences in social motivation underlie reduced social attention in both anorexia nervosa and autism spectrum disorder.