Burnout and decreased well-being among primary care physicians threaten workforce sustainability and health outcomes. Understanding how primary care physician burnout and its mitigators differ across countries could inform policy changes, but evidence is limited. Using 2012-22 survey data from primary care physicians in the United States and nine other high-income countries, we found that shares reporting stress rose across countries. By 2022, the US had one of the highest shares of primary care physicians reporting burnout (44 percent). Switzerland (18 percent) and the Netherlands (12 percent) had the lowest shares reporting burnout, alongside higher shares with satisfaction and lower shares with stress. Across countries, female physicians had higher odds of burnout, whereas workplace factors-including satisfaction with income and administrative workload-and better care quality were associated with reduced odds of burnout. Efforts to reduce burnout should address disparities by sex and should include systemic supports including quality initiatives, flexible work, and arrangements for patient cross-coverage; in-depth cross-national learning could reveal additional strategies.