Background: Not all pharmacies stock and dispense buprenorphine, potentially complicating continuous access to care for patients with opioid use disorder (OUD). This may become problematic if a patient's primary pharmacy can no longer provide buprenorphine, and the patient cannot locate a new pharmacy. Objectives: To identify how often patients treated with buprenorphine for OUD switch pharmacies and to estimate the association between switching pharmacies and a clinically significant gap in therapy of 7 days or longer. Methods: A retrospective repeated measures longitudinal cohort design was used. Patients initiating treatment with a buprenorphine product indicated for OUD were identified from the 2016-2018 Texas Prescription Monitoring Program. The predictor of interest—switching pharmacies—was defined by comparing the dispensaries used between subsequent prescriptions. The outcome of interest was defined as a gap in medication possession of 7 days or longer on the basis of the National Quality Forum's definition of continuity of pharmacotherapy for OUD. A generalized estimating equation approach was used to estimate a repeated measures logistic regression measuring the association between switching pharmacies and a gap in therapy. Results: Of 13,375 eligible patients, 29.6% switched pharmacies at least once during treatment, and 51.6% of these did so more than once. The median time to initial switch was 30 days (interquartile range: 13-66 days). When patients switched pharmacies, they were significantly more likely to have a gap in therapy of between 7 and 29 days (adjusted odds ratio 1.67 [95% CI 1.57–1.78]). Conclusion: Patients receiving buprenorphine switch pharmacies early and frequently in treatment, which leads to clinically significant gaps in therapy. Although qualitative explanatory work is needed to understand why patients switch pharmacies so often, pharmacists and prescribers must ensure that patients have reliable access to a convenient source of buprenorphine to prevent gaps in therapy.