Emerging research tests the impact of United States Medicaid home and community-based (HCBS) waiver policy on outcomes for people with intellectual and developmental disabilities; however, this body of work has yet to be synthesized. We conducted a scoping review to establish what is known about the impact of Medicaid HCBS policy on the lives of people with intellectual and developmental disabilities. Seven studies met final inclusion criteria. Their findings contribute to preliminary evidence that Medicaid HCBS waivers provide economic benefit at the state and federal level, reduce unmet healthcare needs, increase the likelihood that parents will be able to continue working, and reduce racial disparities in access to care. Additional work should compare HCBS waiver programmes, and their causal pathways, as well as draw international comparisons to similar programming, to determine essential infrastructure needed for a successful HCBS programme.