BACKGROUND: Burnout among primary care physicians, advanced practice clinicians (nurse practitioners and physician assistants [APCs]), and staff is common and associated with negative consequences for patient care, but the association of burnout with characteristics of primary care practices is unknown. OBJECTIVE: To examine the association between physician-, APC- and staff-reported burnout and specific structural, organizational, and contextual characteristics of smaller primary care practices. DESIGN: Cross-sectional analysis of survey data collected from 9/22/2015-6/19/2017. SETTING: Sample of smaller primary care practices in the USA participating in a national initiative focused on improving the delivery of cardiovascular preventive services. PARTICIPANTS: 10,284 physicians, APCs and staff from 1380 primary care practices. MAIN MEASURE: Burnout was assessed with a validated single-item measure. KEY RESULTS: Burnout was reported by 20.4% of respondents overall. In a multivariable analysis, burnout was slightly more common among physicians and APCs (physician vs. non-clinical staff, adjusted odds ratio [aOR] = 1.26; 95% confidence interval [CI], 1.05-1.49, APC vs. non-clinical staff, aOR = 1.34, 95% CI, 1.10-1.62). Other multivariable correlates of burnout included non-solo practice (2-5 physician/APCs vs. solo practice, aOR = 1.71; 95% CI, 1.35-2.16), health system affiliation (vs. physician/APC-owned practice, aOR = 1.42; 95%CI, 1.16-1.73), and Federally Qualified Health Center status (vs. physician/APC-owned practice, aOR = 1.36; 95%CI, 1.03-1.78). Neither the proportion of patients on Medicare or Medicaid, nor practice-level patient volume (patient visits per physician/APC per day) were significantly associated with burnout. In analyses stratified by professional category, practice size was not associated with burnout for APCs, and participation in an accountable care organization was associated with burnout for clinical and non-clinical staff. CONCLUSIONS: Burnout is prevalent among physicians, APCs, and staff in smaller primary care practices. Members of solo practices less commonly report burnout, while members of health system-owned practices and Federally Qualified Health Centers more commonly report burnout, suggesting that practice level autonomy may be a critical determinant of burnout.