People with intellectual and developmental disabilities (IDD) often have higher rates of comorbid mental health conditions compared to the general population. Yet, many people with IDD also have unmet needs for mental and behavioral health services. The aim of this study was to examine how states provided mental and behavior health, and crisis services to people with IDD in their Home- and Community-Based Services (HCBS) programs, the largest funding mechanism for Long-Term Services and Supports (LTSS) for people with IDD in the United States. We analyzed fiscal year (2021) Medicaid HCBS waivers for people with IDD from across the United States to examine if and how they provided mental and behavior health, and crisis services. States projected spending $968.9 million for mental and behavior health, and crisis services for 190,299 people with IDD. Applied behavior analysis services were provided at greater rates than positive behavior supports and other forms of behavior interventions. While most states provided mental and behavior health, and crisis services in their waivers, there were vast inconsistencies in how they did so, across states, waivers, and services. HCBS are a crucial safety net to ensure people with IDD, especially those who also have mental health disabilities, can live and thrive in their communities.