--- - |2 Summary In this daily diary study, we investigated the within‐person relationship between daily illegitimate tasks and next‐day counterproductive work behavior (CWB). We explored a moderated mediation model where the link between illegitimate tasks and CWB is mediated by daily end‐of‐work anger, with daily time pressure moderating the relationship between illegitimate tasks and end‐of‐work anger. We collected data from 114 full‐time employees across 10 consecutive working days. Results showed that within individuals, daily illegitimate tasks positively predicted next‐day CWB, and the relationship was mediated by daily end‐of‐work anger. Further, daily time pressure moderated the relationship between daily illegitimate tasks and daily end‐of‐work anger with the relationship being stronger when daily time pressure was high. - Journal of Organizational Behavior, Volume 39, Issue 8, Page 911-921, October 2018.