The current study compared adaptive and cognitive skills, and autism severity of toddlers with an autism spectrum disorder (ASD) diagnosis under DSM-IV but not DSM-5 criteria (DSM-IV only group) to those who met autism criteria under both diagnostic systems (DSM-5 group) and to those without ASD (non-ASD group). The toddlers in the DSM-IV only group were less delayed on various domains of adaptive (Communication, Socialization) and cognitive (Expressive and Receptive language, Fine Motor, Visual Reception) skills, and had less severe symptoms of ASD than the DSM-5 group. Thus, they might have the best potential for successful intervention. The DSM-IV only group did not differ from the non-ASD group in any adaptive or cognitive skills except for socialization skills, the hallmark of ASD.