Abstract: Objective To investigate the mental health status and identify stressors among resident physicians in the Emergency Department (ED), and to provide baseline data for the “3M Mental Care Empowerment Program”. Methods An explanatory sequential mixed-methods design was adopted. A questionnaire survey was conducted among ED residents at Peking Union Medical College Hospital from September 2025 to February 2026 using six standardized scales to assess mental health outcomes. Positive screening rates for depressive symptoms, anxiety symptoms, sleep disturbances, and high burnout were calculated, and levels of general self-efficacy and psychological resilience were evaluated. Correlations among scale scores were analyzed using Spearman’s rank correlation coefficient. Semi-structured interviews were subsequently performed to elaborate on and interpret the quantitative findings. Results A total of 44 ED residents were enrolled, of whom 40 participated in the interviews. The positive screening rates were 34.1% (15/44) for depressive symptoms, 15.9% (7/44) for anxiety symptoms, 59.1% (26/44) for sleep disturbances, and 13.6% (6/44) for high burnout. The mean score on the General Self-Efficacy Scale was 28.3±5.0 (out of 40), and the mean score on the Connor-Davidson Resilience Scale was 63.3±12.7 (out of 100). Spearman correlation analysis revealed that general self-efficacy was moderately and negatively correlated with depressive symptoms (r=-0.533, P<0.001), anxiety symptoms (r=-0.453, P=0.002), and emotional exhaustion (r=-0.419, P=0.005), and was moderately correlated with sleep quality (reverse-scored scale) in the positive direction (r=-0.402, P=0.007). Qualitative interviews identified five core thematic stressors: clinical competency-related anxiety, research and graduation pressures, doctor-patient communication and interpersonal challenges, night shifts and circadian rhythm disruption, and the protective role of social support networks. Conclusions ED residents at Peking Union Medical College Hospital face considerable mental health challenges. General self-efficacy, psychological resilience, and social support networks serve as important protective correlates against psychological distress and stressors. This study provides baseline data and evidence-based support for the targeted implementation of the “3M Mental Care Empowerment Program”