Background: Despite widespread implementation of policies to address mistreatment, the proportion of medical students who experience mistreatment during clinical training is significantly higher than the proportion of students who report mistreatment. Understanding barriers to reporting mistreatment from students’ perspectives is needed before effective interventions can be implemented to improve the clinical learning environment.Objective: We explored medical students’ reasons for not reporting perceived mistreatment or abuse experienced during clinical clerkships at the David Geffen School of Medicine at UCLA (DGSOM).Design: This was a sequential two-phase qualitative study. In the first phase, we analyzed institutional survey responses to an open-ended questionnaire administered to the DGSOM graduating classes of 2013–2015 asking why students who experienced mistreatment did not seek help or report incidents. In the second phase, we conducted focus group interviews with third- and fourth-year medical students to explore their reasons for not reporting mistreatment. In total, 30 of 362 eligible students participated in five focus groups. On the whole, 63% of focus group participants felt they had experienced mistreatment, of which over half chose not to report to any member of the medical school administration. Transcripts were analyzed via inductive thematic analysis.Results: The following major themes emerged: fear of reprisal even in the setting of anonymity; perception that medical culture includes mistreatment; difficulty reporting more subtle forms of mistreatment; incident is not important enough to report; reporting process damages the student–teacher relationship; reporting process is too troublesome; and empathy with the source of mistreatment. Differing perceptions arose as students debated whether or not reporting was beneficial to the clinical learning environment.Conclusions: Multiple complex factors deeply rooted in the culture of medicine, along with negative connotations associated with reporting, prevent students from reporting incidents of mistreatment. Further research is needed to establish interventions that will help identify mistreatment and change the underlying culture.