Novel management strategies for autism spectrum disorder (ASD) propose providing interventions before diagnosis. We performed a cost-effectiveness analysis comparing the costs and dependency-free life years (DFLYs) generated by pre-diagnosis intensive Early Start Denver Model (ESDM-I); pre-diagnosis parent-delivered ESDM (ESDM-PD); and the Ontario Status Quo (SQ). The analyses took government and societal perspectives to age 65. We assigned probabilities of Independent, Semi-dependent or Dependent living based on projected IQ. Costs per person (in Canadian dollars) were ascribed to each living setting. From a government perspective, the ESDM-PD produced an additional 0.17 DFLYs for $8600 less than SQ. From a societal perspective, the ESDM-I produced an additional 0.53 DFLYs for $45,000 less than SQ. Pre-diagnosis interventions targeting ASD symptoms warrant further investigation.