The Affordable Care Act will dramatically increase the number of Americans with Medicaid coverage for substance abuse treatment (SAT). Currently, few SAT providers accept Medicaid, and consequently, there is concern that newly-eligible Medicaid enrollees will have difficulty finding SAT providers willing to serve them. However, little is known about why few SAT providers accept Medicaid. In response, this study examines how features of state Medicaid coverage for SAT, including benefits, eligibility, and oversight, are associated with Medicaid acceptance among SAT providers. Medicaid acceptance was positively associated with the number of SAT services covered, and the number of optional categorical expansions implemented by the state. Requirements for physician involvement were associated with lower odds of acceptance. The results suggest that more generous Medicaid coverage may encourage SAT providers to accept Medicaid, but regulatory policies may inhibit their ability to do so.