OBJECTIVE We aimed to clarify the relationship between assertiveness and burnout among nurse managers at university hospitals. METHODS The directors at three university hospitals agreed to cooperate with our study. During a one-month period from May to June 2007, a self-administered questionnaire was distributed to 203 nurse managers (head and sub-head nurses). The Japanese version of the Rathus Assertiveness Schedule (J-RAS) and the Japanese version of the Maslach Burnout Inventory (MBI) were used as scales. Burnout was operationally defined as a total MBI score in the highest tertile. RESULTS Valid responses were obtained from 172 nurse managers. The mean J-RAS score of the burnout group (-14.3) was significantly lower than that of the non-burnout group (-3.3). Responses about work experience and age showed no significant group difference. Total MBI score was inversely correlated with J-RAS score (R = -0.30, P < 0.01). Multiple logistic regression analyses indicated a decrease in the risk of burnout by 26% (0.74 times) for every 10 point increase in the J-RAS score, and by 60% (0.40 times) for greater satisfaction with own care provision. CONCLUSIONS The results suggest that increasing assertiveness and satisfaction with own care provision contributes to preventing burnout among Japanese nurse managers.