Background: People with intellectual and developmental disabilities' (IDD's) health is largely dependent on the government services they receive. Medicaid managed care has emerged as one mechanism used to provide services to people with disabilities in an attempt to reduce costs. In managed care, there has been an emphasis on reducing emergency department visits and hospital admissions in an effort to reduce expenditures. Objective: The purpose of this exploratory study was to examine the impact social determinants of health -"conditions in the environments in which people are born, live, learn, work, play, worship, and age that affect a wide range of health, functioning, and quality-of-life outcomes and risks" (n.p.)(1) - had on the emergency department utilization of people with IDD. Methods: We had the following research question: what is the relationship between social determinants and emergency department utilization (visits) among adults with IDD? To explore this research question, a negative binomial regression analysis was used with secondary social determinant outcomes data (from Personal Outcome Measures (R)) and emergency department visit data from a random sample of 251 people with IDD. We also examined relationships with participants' demographics. Results: Our findings revealed for every one unit increase in the number of social determinant outcomes present, there was a 7.97% decrease in emergency department visits. There were also significant relationships between emergency department visits, and complex support needs, intellectual disability level, primary communication method, and residence type. Conclusions: Social determinants are critical to promote the quality of life and health equity of people with IDD. (C) 2020 Elsevier Inc. All rights reserved.