--- - |2 Abstract We integrate relative deprivation and broaden and build theories to develop a process‐based model of perceived overqualification and its relationship with new employee adjustment via “broaden and build” mechanisms (i.e., reciprocal relationships between initial status and change trajectories in work‐related positive affect and perceived job autonomy). Additionally, we examine how new employee proactive personality may influence this process. Analyses of weekly survey responses from 331 new employees of a large financial institution throughout their first 90 days of employment revealed that those who felt overqualified generally experienced less work‐related positive affect and perceived less job autonomy when beginning their jobs (assessed the first week of employment) than their more qualified counterparts. Moreover, initial levels of perceived job autonomy were positively associated with adjustment outcomes (assessed at 90 days of employment) via linear change in positive affect over time (assessed weekly, up to 8 weeks of employment). These findings suggest that perceived overqualification may negatively influence newcomer adjustment by stunting broaden and build processes. However, proactive personality attenuated this effect. Theoretical and practical implications are discussed. - Personnel Psychology, EarlyView.