Compare developmental profiles and core ASD symptom manifestation between male and female toddlers with DSM-5 ASD. Retrospective record review of 500 toddlers (79% male) at time of ASD diagnosis. There were no differences in developmental functioning between males and females. When adjusting for multiple comparisons, sex differences were only noted for sensory seeking behavior occurring at a higher frequency in females. Overall, there were no significant differences in demographic characteristics, developmental functioning, or manifestation of core ASD symptoms between males versus female toddlers at the time of DSM-5 ASD diagnosis.