Although the importance of nurses’ service behaviors has been increasingly emphasized, few studies accounted for how organizational or individual antecedents affect nurses’ psychological processes to implement service behaviors. Additionally, they mainly focused on the one side of roleprescribed service behavior and ignored the effect on extra-role service behavior. This study seeks to explore the relationship between ethical climate and nurses’ service behaviors from a comparative view, of the role-prescribed and extra-role service behavior and examine the mediating effect of nurses’ professional wellbeing (as characterized by positive attitudes toward work, specifically harmonious work passion and obsessive work passion). Survey data from 378 nurses in China indicate that nurses’ harmonious work passion mediated the effects of ethical climate on both their role-prescribed and extra-role service behavior; however, obsessive work passion only mediated the effect of ethical climate on roleprescribed service behavior. Managerial implications and future research directions are discussed in this study.