ImportanceApproximately 60% of women physicians in emergency medicine (EM) experience gender-based discrimination (GBD). Women physicians are also more likely to experience GBD than men physicians, particularly from patients, other physicians, or nursing staff.ObjectiveTo describe the responses of men who are academic department chairs in EM to GBD directed toward a woman colleague.Design, Setting, and ParticipantsThis qualitative study was a secondary data analysis drawn from interviews of men EM academic department chairs at 18 sites who participated in a qualitative descriptive study between April 2020 and February 2021 on their perceptions of the influence of gender and leadership in academic medicine. Narrative data related to GBD were extracted and coded using conventional content analysis. Codes were clustered into themes and subthemes and summarized. Data were analyzed from November to December 2021.ExposureSemistructured interviews conducted via teleconferencing.Main Outcomes and MeasuresQualitative findings identifying experiences witnessing or learning about incidents of GBD against women colleagues, the impact of these observations, and personal or leadership actions taken in response to their observations.ResultsAll 18 men participants (mean [SD] age, 52.2 [7.5] years; mean [SD] time as a department chair, 7.2 [5.1] years) discussed witnessing or learning about incidents of GBD against women colleagues. The participant narratives revealed 3 themes: emotional responses to GBD, actions they took to address GBD, and reasons for not taking action to address GBD. When witnessing GBD, participants felt anger, disbelief, guilt, and shame. To take action, they served as upstanders, confronted and reported discrimination, provided faculty development on GBD, or enforced “zero-tolerance” policies. At times they did not take action because they did not believe the GBD warranted a response, perceived a power differential or an unsupportive institutional culture, or sought self-preservation.Conclusions and RelevanceIn this qualitative study of men physician leaders, we found all participants reported feeling troubled by GBD against women colleagues and, if possible, took action to address the discrimination. At times they did not take action because of unsupportive workplace cultures. These findings suggest that institutional culture change that supports the interventions of upstanders and does not tolerate GBD is needed.