BACKGROUND: Physicians' attitudes can be critical in quality end-of-life care. However, the determinants of the attitudes and whether the attitudes can be modified remain unclear. OBJECTIVES: To investigate factors correlated with physicians' positive attitudes toward end-of-life care and whether these attitudes are modifiable through acquired factors (e.g., education or mentorship). DESIGN: A nationwide survey was conducted in 300 institutions and selected randomly from 1037 clinical training hospitals in Japan. PARTICIPANTS: From each selected institution, two resident physicians of postgraduate year (PGY) 1 or 2 and two clinical fellows from PGY 3-5 were requested to answer the survey. MEASUREMENTS: The primary outcome was the Frommelt Attitudes Toward the Care of the Dying (FATCOD) scale score. Factors (e.g., the respondents' age, sex, number of years of clinical experience, training environment, religion, and beliefs around death) were examined for correlation with FATCOD score. RESULTS: In all, 198 physicians and 134 clinical fellows responded to the survey (response rate: 33.0% and 22.3%, respectively). Factors with the strongest correlation with FATCOD scores were mostly unmodifiable factors (e.g., being female and one's beliefs around death). Modifiable factors were also identified-number of patient deaths experienced, level of interest in palliative care, availability of support from senior mentors, and frequency of consultation with nonphysician medical staff. CONCLUSION: Physicians' attitudes toward end-of-life care correlate more strongly with nonmodifiable factors, but attitudes can be meaningfully improved via mentoring by senior physicians. Future studies are warranted to determine the effective interventions to foster positive attitudes among physicians involved in end-of-life care.