This study explored the effects of trust in a supervisor (TIS) on social loafing behaviors of employees. In addition, this study examined the mediating effect of perceived organizational support (POS) on the relationship between trust in a supervisor and employees’ social loafing behaviors. It also examined the moderating effects of perceived organizational politics (POP) on the relationship between TIS and POS, TIS and social loafing behaviors, and POS and social loafing behaviors. Data were collected from local government employees in Korea, and the final sample was 260. Our results indicate that trust in a supervisor has indirect negative effects on social loafing behaviors mediated by POS. In addition, it was found that the effects of TIS on POS and POS on social loafing behaviors were moderated by POP. The results of this study contribute to the extant literature on social loafing behaviors. Moreover, the findings imply that political behaviors in organizations might induce social loafing behaviors.