Autism spectrum disorder (ASD) is more common in males than females. An underrepresentation of females in the ASD literature has led to limited knowledge of differences in social function across the sexes. Investigations of face perception represent a promising target for understanding variability in social functioning between males and females. The current study analyzed electrophysiological brain recordings during face perception to investigate sex differences in the neural correlates of face perception and their relationship to social function. Event related potentials (ERP) were recorded from children with ASD while viewing faces, inverted faces, and houses. Relative to males, females showed attenuated response at an ERP marker of face perception, the N170. Among females, but not males, atypical face response was associated with symptom severity. Observed sex differences reflect influential differences in social information processing, and impairment in these features correlates with deficits in social information processing in females, but not males, with ASD. These findings hold significance for future treatment protocols, which should account for differences in males and females with ASD in clinical presentation and neural phenotypes.