Empirical studies should deal with the very important issue of organizational justice and citizenship behavior in contingent workers. This study aimed to determine the role of the leader-member exchange (LMX) theory and perceived organizational support (POS) as a mediator separately against the relationship between organizational justice (OJ) and organizational citizenship behaviors (OCB). The population of the study included 150 non-permanent lecturers at five private universities in Indonesia. Survey methods were used for data collection. Factor analysis output proved that OJ relates to four factors. These four dimensions have various relationships with OCB directed towards the organization (OCBO) and OCB directed towards supervisor (OCBS) separately. The result of the structural equation modeling showed that POS and LMX cannot play a mediating role in the relationship between OJ and OCB in the context of non-regular workers.