<p>Illegitimate tasks are perceived as peripheral to organizational roles, leading to feelings of offense and negatively impacting employees’ self-esteem. However, the specific stress perception responses to these tasks have not been clearly considered. Grounded in the transactional model of stress, this study aims to clarify two cognitive appraisals by which illegitimate tasks affect employee stress perception responses. The first path examines whether illegitimate tasks negatively impact employee organizational-based self-esteem via threat appraisal. The second path investigates whether illegitimate tasks positively relate to employee frustration via hindrance appraisal. Additionally, the study assesses how these pathways are influenced by employee performance-prove goal orientation. This study employs a time-lagged design, collecting data at two-time points from 238 full-time employees in China. Path analysis was used to test the proposed hypotheses. The findings revealed that employees appraise illegitimate tasks as both threat and hindrance, with threat appraisals significantly diminishing their organizational-based self-esteem. Furthermore, performance-prove goal orientation was found to positively moderate both the relationships between illegitimate tasks and cognitive appraisals, as well as the effect of illegitimate tasks on organizational-based self-esteem through threat appraisals. These findings offer valuable management insights for Chinese enterprises on optimizing task allocation systems.</p>