We examined the late positive potential (LPP) event related potential in response to social and nonsocial stimuli from youths 9 to 19 years old with (n = 35) and without (n = 34) ASD. Social stimuli were faces with positive expressions and nonsocial stimuli were related to common restricted interests in ASD (e.g., electronics, vehicles, etc.). The ASD group demonstrated relatively smaller LPP amplitude to social stimuli and relatively larger LPP amplitude to nonsocial stimuli. There were no group differences in subjective ratings of images, and there were no significant correlations between LPP amplitude and ASD symptom severity within the ASD group. LPP results suggest blunted motivational responses to social stimuli and heightened motivational responses to nonsocial stimuli in youth with ASD.