In recent years, scholars and practitioners have shared an increasing interest in exploring the impact of star employees. However, most focus has been on the association between star employees and non-stars, teams, or organizations, with little work concerning the potential upward influence of star employees on their immediate supervisors. Combining star employee literature and the cognitive appraisal theory of stress, this research develops a mediated moderation model to examine when and how star employees trigger supervisors' self-interested behaviors. Results from a scenario-based experiment and a time-lagged multi-source field survey (204 star-supervisor dyads) revealed that supervisors are likely to be threatened by star employees when they feel a low level of trust from their managers. Consequently, supervisors tend to engage in self-interested behaviors as a means of self-protection. These findings enrich existing star employee literature by focusing on the star-supervisor dyad and provide insight into related management practices.