BACKGROUND: Prescription opioid overprescribing is a focal point for legislators, but little is known about opioid prescribing patterns of primary care nurse practitioners (NPs) and physician assistants (PAs). OBJECTIVE: To identify prescription opioid overprescribers by comparing prescribing patterns of primary care physicians (MDs), nurse practitioners (NPs), and physician assistants (PAs). DESIGN: Retrospective, cross-sectional analysis of Medicare Part D enrollee prescription data. PARTICIPANTS: Twenty percent national sample of 2015 Medicare Part D enrollees. MAIN MEASURES: We identified potential opioid overprescribing as providers who met at least one of the following:(1) prescribed any opioid to > 50% of patients, (2) prescribed ≥ 100 morphine milligram equivalents (MME)/ day to > 10% of patients, or (3) prescribed an opioid > 90 days to > 20% of patients. KEY RESULTS: Among 222,689 primary care providers, 3.8% of MDs, 8.0% of NPs, and 9.8% of PAs met at least one definition of overprescribing. 1.3% of MDs, 6.3% of NPs, and 8.8% of PAs prescribed an opioid to at least 50% of patients. NPs/PAs practicing in states with independent prescription authority were > 20 times more likely to overprescribe opioids than NPs/PAs in prescriptionrestricted states. CONCLUSIONS: Most NPs/PAs prescribed opioids in a pattern similar to MDs, but NPs/PAs had more outliers who prescribed high-frequency, high-dose opioids than did MDs. Efforts to reduce opioid overprescribing should include targeted provider education, risk stratification, and state legislation.