Abstract As a pervasive workplace phenomenon in service organizations, knowledge hiding can cause serious economic losses to companies. This study seeks to identify a new interpersonal antecedent of knowledge hiding, specifically workplace ostracism. We further focus on the moderating roles of negative reciprocity beliefs and moral disengagement in the relationship between workplace ostracism and knowledge hiding in service organizations. Using a time-lagged research design, we collected data from 253 samples in 17 Chinese hotels. As predicted, we found that workplace ostracism was positively related to hospitality employees’ evasive hiding and playing dumb, but not related to rationalized hiding. In addition, we supported a hypothesized three-way interaction involving workplace ostracism, negative reciprocity beliefs, and moral disengagement on evasive hiding and playing dumb, but not on rationalized hiding. In particular, workplace ostracism was most positively related to evasive hiding and playing dumb when both negative reciprocity beliefs and moral disengagement were high. However, workplace ostracism was not related to evasive hiding and playing dumb when service workers have low levels in either or both.