This study aims to introduce a concept and assess the discretionary job behavior (DJB) of employees in service organizations. Further, it intends to examine the antecedents of DJB. In this study, DJB was defined as a self-directed and self-disciplined behavior wherein employees perceived their discretion in performing their task-oriented job activities. Self-report data was collected from 791 employees working at a retail company. Factor analysis indicated that the employees exhibited DJB in four behavioral domains: (a) promotion of the organizational image to outsiders, (b) compliance with organizational values, (c) efforts to attain a goal, and (d) helping coworkers. Using covariance structure analysis, the authors demonstrated that each behavior had its own relationship with the four antecedents (psychological sensitivity on the company’s reputation, organizational value internalization, the need for financial reward, and the need for interpersonal reward.