Employees perceive illegitimate tasks as inappropriate assignments because such tasks are beyond what they expect to do in any given job position. Extant literature indicates that, in addition to creating psychological strain and reducing well-being, illegitimate task assignments can result in counterproductive work behavior (CWB). This study extends the literature by examining whether illegitimate tasks may lead to two specific forms of CWB targeting organizations: destructive voice and time theft. To understand how and when this happens, we investigate the mediating role of moral disengagement and the moderating role of psychological entitlement. Survey results based on 258 supervisor–subordinate dyads in China reveal that illegitimate tasks are positively related to destructive voice and time theft through moral disengagement. Furthermore, psychological entitlement strengthens the positive relationship between illegitimate tasks and moral disengagement and the indirect effect of illegitimate tasks on destructive voice and time theft. Overall, the findings provide insightful theoretical and managerial implications for research related to illegitimate tasks and CWB.