Adults with intellectual and developmental disabilities (IDD) are known to experience significant health disparities; however, few studies have described anti-hypertensive medication adherence in this population. Using administrative data from South Carolina from 2000–2014, we evaluated the odds of adherence to anti-hypertensive medication among a cohort of adults with IDD and hypertension. Approximately half (49.5%) of the study cohort were adherent to anti-hypertensive medication. Those who lived in a supervised residence, had a Medicaid waiver, and had more frequent contact with a primary care provider were more likely to be adherent. Organizations that serve people with IDD have an opportunity to increase adherence by educating these individuals, their family members, and caregivers about the importance of adherence to anti-hypertensive medication.