This study examined the antecedents of psychological empowerment at hospital organizations, and also examined their differential effects among occupational groups within hospitals: doctors, nurses, engineers, and administrative workers. Various variables for multi-level factors were examined as antecedents: tenure, income, work centrality, and career goal as personal factors, job variety, job clarity, job significance, and job fitness as job factors, and security, reward justice, and organizational support as organizational factors. Data were collected from 8 national university hospitals, and 1,289 data were used for final analysis. For the whole groups, all antecedents except reward justice had significant effects on, and explained large amount of variance of empowerment. Results from the analysis for each occupational group showed that income, career goal, and job significance had significant effects on empowerment at all occupational groups, while reward justice had not at any groups. The effects of other variables depended on occupational groups. 1bis study found some important antecedents of empowerment which have been less considered in previous research: career goal, work centrality, security, and organizational support. The finding that differential effects of antecedents on empowerment by occupational groups suggests that group characteristics should be considered for studying empowerment. In this study, for example, personal factors rather than both job factors and organizational factors were more effective for empowerment in the engineering group whose job is relatively simple and clear, while job factors were most effective in other groups. The differential effects of antecedents on empowerment by occupational groups also have practical implications for improvement of empowerment at hospitals. For empowerment, personnel management efforts would be more required for administrative workers than other occupational groups, because they perceived least job clarity, job significance, job fitness among the groups, all of which were found to be important determinants of empowerment for them.