Using the 2008-2013 Medicaid Analytic eXtract files, this retrospective cohort study was to evaluate the effect of Medicaid home and community-based services (HCBS) waiver programs on emergency department (ED) utilizations among youth with autism spectrum disorder (ASD). Our study showed that the annual ED utilization rates were 13.5% and 18.8% for individuals on autism specific and intellectual and developmental disabilities (IDD) waivers respectively, vs. 28.5% for those without a waiver. Multivariable logistic regression showed that, compared to no waiver, autism specific waivers (adjusted odds ratio: 0.62; 95% Confidence Interval: [0.58-0.66]) and IDD waivers (0.65; [0.64-0.66]) were strongly associated with reduced ED. These findings suggest that HCBS waivers are effective in reducing the incidence of ED visits among youth with ASD.