Study Objective: The influence of workplace mistreatment on the well-being and career satisfaction of emergency medicine residents is unknown. This study examined the relationships between burnout, career choice regret, and workplace mistreatment in a national sample of emergency medicine residents., Methods: This was a secondary analysis of a survey study on the prevalence of workplace mistreatment among emergency residents. Residents who reported emotional exhaustion or depersonalization at least once per week were considered to have burnout. Residents who reported dissatisfaction with their decision to become an emergency physician were considered to have career choice regret. Respondents also reported the type (discrimination, abuse, sexual harassment) and frequency of mistreatment over the academic year. Multivariable logistic regression, adjusting for program characteristics, was used to examine resident characteristics associated with burnout and career choice regret, with the frequency of mistreatment as a covariate., Results: Of the 8,162 eligible residents, 7,680 (94.1 %) participated. About a third of respondents reported burnout (2,188 of 6,902, 31.7%), whereas a minority (224 of 6,923, 3.2%) reported career choice regret. Of the 7,087 responses on mistreatment frequency, 2,117 (29.9%) reported "a few times per year," and 1,296 (18.3%) reported "a few times per month or more." Compared with residents who never experienced mistreatment, residents who reported increasing frequencies of mistreatment were associated with having burnout-from mistreatment a few times per year (OR [odds ratio],1.6; 99% CI [confidence interval], 1.3 to 1.9) to a few times per month or more (OR, 3.3; 99% CI, 2.7 to 4.1). Compared with residents without burnout, residents who reported burnout were associated with having career choice regret (OR, 11.3; 99% CI, 7.0 to 18.1). After adjusting for burnout, there were no significant relationships between the frequency of mistreatment and career choice regret., Conclusions: Workplace mistreatment is associated with burnout, but not career choice regret, among emergency medicine residents. Efforts to address workplace mistreatment may improve emergency medicine residents' professional well-being., (Copyright © 2022 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.)