Public security, traffic management, and service for the people are the 3 major functions of policing in Taiwan. This definition encompasses not only the traditional job characteristics, but also the level of contextual characteristics and social characteristics because of police work's characteristics and its frequent interaction with the public. Thus, the present study conducted a multilevel model analysis by taking self-efficacy and collective efficacy as the mediating variables. The purpose was to investigate the influences of motivational work characteristics (knowledge-oriented) and social work characteristics (socially and contextually oriented) of work-design model on the police officers' organizational citizenship behavior (OCB), by using first-line police officers in Taiwan as the research objects. The study showed not only that knowledge characteristics will influence the self-efficacy of a police officer and that self-efficacy can in turn influence individual police officers' OCB, but also the contextual effect of social characteristics, contextual characteristics, and collective efficacy on self-efficacy and individuals' OCB. Additionally, there was a crosslevel moderating effect from contextual characteristics on the relationship between knowledge characteristics and self-efficacy and the relationship between self-efficacy and the individuals' OCB. The authors conclude the article with research implications.