With the escalating influence of workplace environment on organizational behavior, this study examined the relationships between workplace ostracism, person–organization fit, perceived organizational support, organizational citizenship behavior, and deviant behavior. Although prior studies have found that workplace ostracism led to negative outcomes, research to date has not been extensive in studying the underlying mechanisms which associate workplace ostracism and its behavioral outcomes. This study investigated the mediating effects of person–organization fit and the moderating effects of perceived organizational support between person–organization fit with organizational citizenship behavior and deviant behavior. Using a sample consisting of 249 employees in various organizations in South Korea, this study found person–organization fit to mediate the relationships between workplace ostracism and both organizational citizenship behavior and deviant behavior, while perceived organizational support moderated the link between person–organization fit and both organizational citizenship behavior and deviant behavior.