Background: Nurse practitioners are increasingly being integrated into primary care delivery to help meet the growing demand for primary care. It is therefore important to understand nurse practitioners' productivity in primary care practice. Purpose: We examined nurse practitioners' clinical productivity in regard to number of patients seen per week, whether they had a patient panel, and patient panel size. We further investigated practice characteristics associated with their clinical productivity. Methods: We conducted cross-sectional analysis of the 2012 National Sample Survey of Nurse Practitioners. The sample included full-time primary care nurse practitioners in ambulatory settings. Multivariable survey regression analyses were performed to examine the relationship between practice characteristics and nurse practitioners' clinical productivity. Results: Primary care nurse practitioners in ambulatory settings saw an average of 80 patients per week (95% confidence interval [CI]: 79-82), and 64% of them had their own patient panel. The average patient panel size was 567 (95% CI: 522612). Nurse practitioners who had their own patient panel spent a similar percent of time on patient care and documentation as those who did not. However, those with a patient panel were more likely to provide a range of clinical services to most patients. Nurse practitioners' clinical productivity was associated with several modifiable practice characteristics such as practice autonomy and billing and payment policies. Discussions: The estimated number of patients seen in a typical week by nurse practitioners is comparable to that by primary care physicians reported in the literature. However, they had a significantly smaller patient panel. Nurse practitioners' clinical productivity can be further improved.