Abstract For children with autism spectrum disorder (ASD), a lifelong neurodevelopmental condition, assessment and treatment services vary widely across Canada—potentially creating inequities. To highlight this, the Preschool Autism Treatment Impact study compared children’s services and outcomes in New Brunswick (NB) and Nova Scotia (NS). Diagnostic practices, service delivery models, wait times, and treatment approaches differed, as did children’s 1-year outcomes and costs for families and the public sector. Considering NB and NS strengths, we suggest that an optimal system would include: rapid access to high-quality diagnostic and intervention services; adherence to research-informed practice guidelines; interventions to enhance parents’ skills and self-efficacy; and measures to minimize financial burdens for families. Our results also suggest that provinces/territories must do more to ensure equitable access to effective services, including sharing and reporting on national comparative data. Canadian children with ASD deserve access to effective and consistent services, no matter where they live.