Background and Objectives Despite high comorbidity between substance use disorders and other mental health diagnoses, there is a paucity of literature on buprenorphine treatment outcomes in outpatient mental health settings. This study aimed to identify rates and predictors of outpatient buprenorphine treatment retention in a Behavioral Health Clinic (BHC). Methods This retrospective cohort study of adults on buprenorphine used multiple logistic regression to identify clinical and demographic factors associated with 1‐ and 2‐year treatment retention and buprenorphine adherence. Results Of 321 subjects, 169 (52.6%) were retained in treatment for at least 1 year; 114 (35.5%) were retained for 2 years or more. Buprenorphine adherence was 95.8% and 97.3% for 1‐ and 2‐year retention groups, respectively. Predictors of 1‐year retention included benzodiazepine co‐prescription (adjusted odds ratio [AOR] = 2.4; 95% CI [1.30, 4.55]), having a diagnosis of other mood disorder (AOR = 3.4; [1.95, 5.98]), or nicotine use disorder (AOR = 2.4; [1.35, 4.27]). Predictors of 2‐year retention included female gender (AOR = 2.1; [1.16, 3.73]), having a diagnosis of depressive disorder (AOR = 4.6; [1.49, 14.29]), other mood disorder (AOR = 3.6; [1.88, 6.88]), or nicotine use disorder (AOR = 2.0; [1.13, 3.52]). Discussion and Conclusion During the study period, 52.7% and 35.5% of BHC patients treated with buprenorphine were retained for 1 and 2 years, respectively, comparable to the studies performed within primary care. Providing buprenorphine treatment within mental health clinics may serve patients who are already engaged with mental health providers but are reluctant to start new treatment within another treatment setting. Scientific Significance Identifying common predictors of retention can help determine which patients require additional substance use treatment support. (Am J Addict 2019;28:339–346)