A majority of children with special health care needs (CSHCN) have behavioral health conditions. Black and Hispanic CSHCN are more likely to have these health conditions and less likely to have them diagnosed and treated compared with other CSHCN. Differences in access to care contribute to variation in use of behavioral health treatment, and limited insurance coverage leads to poor health outcomes among CSHCN. Early identification and treatment for behavioral health conditions is critical to support the health and well-being of CSHCN over their lifetimes. Yet, families of CSHCN often experience difficulties in accessing needed behavioral health services. Differences in behavioral health outcomes can be mitigated by expanding insurance coverage and encouraging use of treatment. Addressing these mechanisms early in life is critical to improve health outcomes over the entire life course. There is mixed evidence on the extent to which health insurance expansions have improved coverage and health service use for CSHCN and subgroups of CSHCN. Other policies, including streamlined or automatic enrollment in Medicaid, have been shown to increase Medicaid enrollment, retention and overall insurance coverage rates, but there is no evidence about the impact of these policies on improving coverage or utilization for CSHCN overall, or subgroups of CSHCN including Black or Hispanic children and children who have mental health conditions. Specific interventions in expanding services may be more effective at improving outcomes for these populations but evidence on the effects of such interventions is limited. More research is needed to understand the extent to which policies can reduce differences in health insurance coverage and behavioral health care utilization among CSHCN subgroups. This study will examine the effects of a policy which could increase insurance coverage and behavioral health service utilization among CSHCN: automatic enrollment in Medicaid via Supplemental Security Income (SSI). We propose two complementary analytic approaches, one with nationally representative survey data and one exploiting a natural experiment in Medicaid claims data. We will quantify the effects of Medicaid automatic enrollment via SSI on insurance coverage and behavioral health service use overall and among Black and Hispanic CHSCN; identify the demographics of CSHCN who are newly enrolled in Medicaid due to automatic enrollment policies and examine potential differences in their health needs; and examine how the effects on behavioral health service use, health outcomes, and differences in service use and outcomes evolve over time for newly enrolled CSHCN. Our findings will provide critical insights about how targeted Medicaid automatic enrollment could improve behavioral health outcomes for this CSHCN and subgroups of CSHCN and will contribute to broader understanding of how reducing administrative burden may improve health outcomes for CSHCN.