Supervisors are the primary drivers of performance management; however, little is known about factors that influence their implementation of these systems. The purpose of this study was to investigate how a supervisor individual difference—implicit person theory (IPT)—differentially predicts supervisor behaviors during, as well as both supervisor and employee reactions to appraisal interviews. In Study 1, MBA students reported their supervisors’ behaviors during their most recent performance appraisal interview (Time 1) as well as their subsequent reactions (i.e., perceived satisfaction, utility, success, supervisor support; Time 2). Their supervisors completed a measure assessing their own IPT (Time 3). Findings suggest that supervisors’ task-oriented behaviors predicted perceived satisfaction, utility, and success of the appraisal interviews, while supervisor’ relational-oriented behaviors predicted perceived supervisor support. In Study 2, supervisors recruited via MTurk completed all measures from Study 1 except perceived success. Results suggest that IPT was positively related to task-oriented behaviors and perceived utility, task-oriented behaviors mediated the relationship between IPT and all three reaction measures (i.e., perceived satisfaction, utility, and supervisor support), and relational-oriented behaviors significantly predicted supervisors’ perceived support. Overall, findings suggest that supervisors who believe people can change (hold a more incremental IPT) display more task-oriented behaviors during and see more utility in appraisal interviews. Additionally, task-oriented behaviors emerged as the key mechanism linking supervisors’ IPT and reactions to appraisal interviews. These findings demonstrate that supervisor individual differences, such as IPT, can influence performance appraisal and management outcomes.