Background: Clinical pharmacist practitioners (CPPs) play an increasingly important role in interdisciplinary care for patients with substance use disorders (SUDs). However, CPPs’ scope of practice varies substantially across clinics and settings. Objectives: We sought to describe CPP practices and activities within an interdisciplinary, team-based primary care clinic dedicated to treat Veterans with histories of substance use disorders, experience of homelessness, high medical complexity, and other vulnerabilities. Methods: We conducted a retrospective cohort study of CPP activities using Department of Veterans Affairs (VA) administrative data in 2019. Results: CPPs provided care for 228 patients, including 766 in-clinic visits, 341 telephone visits, and 626 chart reviews, with an average of 2.5 hours spent per patient per year. Patients seen by CPPs frequently experience mental health conditions and SUDs, including depression (66%), post-traumatic stress disorder (52%), opioid use disorder (OUD) (45%), and alcohol use disorder (44%). CPPs managed buprenorphine medications for OUD or chronic pain in 76 patients (33%). Most CPP interventions (3330 total) were for SUDs (33%), mental health conditions (24%), and pain management (24%), with SUD interventions including medication initiation, dose changes, discontinuations and monitoring. As part of opioid risk mitigation efforts, CPPs queried the state’s prescription drug monitoring program 769 times and ordered 59 naloxone kits and 661 lab panels for empaneled patients. Conclusion: CPPs managed a high volume of vulnerable patients and provided complex care within an interdisciplinary primary care team. Similar CPP roles could be implemented in other primary care settings to increase access to SUD treatment.