The Affordable Care Act (ACA) was expected to benefit patients with substance use disorders, including opioid use disorders (OUDs). This study examined buprenorphine use and health services utilization by patients with OUDs pre- and post-ACA in a large health care system. Using electronic health record data, we examined demographic and clinical characteristics (substance use, psychiatric and medical conditions) of two patient cohorts using buprenorphine: those newly enrolled in 2012 (“pre-ACA,” N = 204) and in 2014 (“post-ACA,” N = 258). Logistic and negative binomial regressions were used to model persistent buprenorphine use, and to examine whether persistent use was related to health services utilization. Buprenorphine patients were largely similar pre- and post-ACA, although more post-ACA patients had a marijuana use disorder (p < .01). Post-ACA patients were more likely to have high-deductible benefit plans (p < .01). Use of psychiatry services was lower post-ACA (IRR: 0.56, p < .01), and high-deductible plans were also related to lower use of psychiatry services (IRR: 0.30, p < .01). The relationship between marijuana use disorder and prescription opioid use is complex, and deserves further study, particularly with increasingly widespread marijuana legalization. Access to psychiatry services may be more challenging for buprenorphine patients post-ACA, especially for patients with deductible plans.