<p>Illegitimate tasks, perceived as unreasonable or outside formal role expectations, represent an overlooked academic stressor in graduate education that may undermine research collaboration and well-being. Drawing on Conservation of Resources (COR) theory and the Cognitive Appraisal Theory of Stress, we examine whether illegitimate tasks increase graduate students’ knowledge hiding through relative deprivation, and whether delay of gratification buffers this effect. Study 1 employed a two-stage questionnaire survey (<i>N</i> = 492), and Study 2 used a vignette experiment (<i>N</i> = 216) to reduce common method bias. Results from both studies revealed that illegitimate tasks were positively associated with knowledge hiding, with relative deprivation partially mediating this relationship. Additionally, delay of gratification moderated the relationship between illegitimate tasks and relative deprivation, buffering negative emotional responses. These findings underscore the role of task-related stressors in academic contexts and highlight the buffering effect of self-regulatory traits on maladaptive coping behaviors.</p>