Emerging research in the idiosyncratic deals literature is to examine its negative effects. Thus far, much remains unknown about how and when idiosyncratic deals are associated with employee creative process engagement. Invoking fairness heuristic theory and trait activation theory, we propose and test a model that coworker's idiosyncratic deals have a negative association with witness's creative process engagement through psychological contract violation. Furthermore, we theorize and test the combination of the responsibility for change and perceived exploitative leadership as important boundary conditions, associate interact with coworker's idiosyncratic deals to strengthen the positive impact on psychological contract violation, thereby reducing witness's creative process engagement. We use two time-lagged studies to provide support for these mediation and moderation effects, and also discuss the theoretical and practical implications of these findings.