Policymakers and business leaders often use peer comparison information-showing people how their behavior compares to that of their peers-to motivate a range of behaviors. Despite their widespread use, the potential impact of peer comparison interventions on recipients' well-being is largely unknown. We conducted a 5-mo field experiment involving 199 primary care physicians and 46,631 patients to examine the impact of a peer comparison intervention on physicians' job performance, job satisfaction, and burnout. We varied whether physicians received information about their preventive care performance compared to that of other physicians in the same health system. Our analyses reveal that our implementation of peer comparison did not significantly improve physicians' preventive care performance, but it did significantly decrease job satisfaction and increase burnout, with the effect on job satisfaction persisting for at least 4 mo after the intervention had been discontinued. Quantitative and qualitative evidence on the mechanisms underlying these unanticipated negative effects suggest that the intervention inadvertently signaled a lack of support from leadership. Consistent with this account, providing leaders with training on how to support physicians mitigated the negative effects on well-being. Our research uncovers a critical potential downside of peer comparison interventions, highlights the importance of evaluating the psychological costs of behavioral interventions, and points to how a complementary intervention-leadership support training-can mitigate these costs.