While employees’ proactive behaviors often benefit organizations, such behaviors may not always be welcomed by supervisors, particularly when they encroach on managerial roles. This research probes into supervisors’ perceptions of employees’ vertical proactive behaviors (VPBs)—proactive actions that overlap with supervisory responsibilities. In Study 1, we developed a scale to measure VPBs. In Study 2, we tested a theoretical model contrasting two perspectives on role boundaries. Based on Social Interdependence Theory, we hypothesized that supervisors perceiving role interdependence with subordinates would respond positively to VPBs. Conversely, Role Congruity Theory suggests that perceived role threat would make supervisors adopt negative responses to VPBs. A two-wave survey from 152 supervisor-subordinate pairs revealed that VPBs indirectly enhanced employees’ promotability through the serial mediation of employees’ role enlargement and supervisors’ reduction of role overload. Additionally, high supervisor trust in employee mitigated perceptions of role threat, supporting Social Interdependence Theory over Role Congruity Theory. These findings highlight the importance of role boundary perception in shaping supervisors’ responses to employees’ proactive behaviors.
