In the United States, health insurance coverage for autism spectrum disorder treatments has been historically limited. In response, as of 2015, 40 states and Washington, DC, have passed state autism insurance mandates requiring many health plans in the private insurance market to cover autism diagnostic and treatment services. This study examined five states’ experiences implementing autism insurance mandates. Semi-structured, key-informant interviews were conducted with 17 participants representing consumer advocacy organizations, provider organizations, and health insurance companies. Overall, participants thought that the mandates substantially affected the delivery of autism services. While access to autism treatment services has increased as a result of implementation of state mandates, states have struggled to keep up with the demand for services. Participants provided specific information about barriers and facilitators to meeting this demand. Understanding of key informants’ perceptions about states’ experiences implementing autism insurance mandates is useful for other states considering adopting or expanding mandates or other policies to expand access to autism treatment services.