PURPOSE: Opioid use disorder is a prevalent and chronic condition that can lead to adverse outcomes if untreated. Medication-assisted treatment (MAT) with buprenorphine in a primary care setting has the potential to increase availability of treatment and reduce harm; however, retention in MAT is key for patient success. This study's purpose was to examine predictors of retention in a MAT program for OUD in a family medicine residency clinic. METHODS: A retrospective chart review was conducted for 238 patients diagnosed with OUD and receiving MAT at a family medicine residency clinic between 2015 to 2017, with visit and prescription data collected through December 2018. Cox-proportional hazards models were used to examine the length of time in treatment. RESULTS: Over three-fourths of our patients were retained for at least 3 months, 69% for at least 6 months, and 48% retained for at least 1 year. Physician continuity of care and having insurance coverage significantly predicted retention and longer duration of treatment. CONCLUSIONS: Continuity of care and having health insurance were key predictors of patient retention in MAT care. Our findings emphasize the clinical significance of maintaining physician continuity of care to improve retention of patients with OUD in MAT programs. Future research could explore what aspects of continuity of care lead to retention in OUD treatment.