Autism spectrum disorder (ASD) diagnosis is based on behavioral presentation; changes in conceptual models or defining behaviors may significantly impact diagnosis and uptake of ASD-specific interventions. The literature examining impact of DSM-5 criteria is equivocal. Toddlers may be especially vulnerable to the stringent requirements of impairment in all three social-communication symptoms and two restricted/repetitive symptoms. Receiver operating characteristic (ROC) curves identified optimal cutoffs for sums of ADOS and ADI-R criteria mapped to each criterion for 422 toddlers. The optimal modification of DSM-5 criteria (sensitivity = 0.93, specificity = 0.74) required meeting the ROC-determined cutoffs for 2/3 Domain A criteria and 1 point for 1/4 Domain B criteria. This modification will help insure that ASD is identified accurately in young children, facilitating ASD-specific early intervention.