Purpose We assessed an educational intervention to reduce the number of emergency department (ED) and inpatient stays for cardiovascular diagnoses, among South Carolina adult Medicaid Members with intellectual and developmental disability and hypertension (Members). Design This Randomized Controlled Trial (RCT) included Members or the person who helped them with their medications (Helpers). Participants, who included Members and/or their Helpers, were randomly assigned to an Intervention or Control group. Setting South Carolina Department of Health and Human Services, which administers Medicaid, identified eligible Members. Sample 412 Medicaid Members - 214 Intervention (54 Members participating directly; 160 Helpers participating in lieu of Members) who received the messages about hypertension and surveys about knowledge and behavior and 198 Controls (62 Members; 136 Helpers) who only received surveys of knowledge and behavior. Intervention Educational intervention about hypertension included a flyer and monthly text or phone messages for one year. Measures Input measures - characteristics of the Members; Outcome measures - hospital emergency department (ED) and inpatient visits for cardiovascular conditions. Analysis Quantile regression tested the association of Intervention/Control group status with ED and inpatient visits. We also estimated models using Zero-inflated Poisson (ZIP) models for sensitivity analysis. Results Participants in the Intervention group with highest baseline hospital use (top 20% ED; top 15% Inpatient) had significant reductions in Year 1 (.57 fewer ED and 2 fewer inpatient days) compared to the Control group. For ED visits, improvement continued in year two. Conclusion The intervention reduced the frequency of cardiovascular disease-related ED visits and Inpatient days for participants in the Intervention group in the highest quantiles of hospital use, and the improvement was better for those who had a Helper.