In this present study, we propose a multilevel research framework within which we identify personality traits as the primary source of the positive influence on leader-member exchange (LMX) through the mechanism of impression management behavior. Data are obtained from 23 branches of a large commercial bank in central Taiwan, with the samples collected from both managers and employees forming 228 manager-employee dyads, and thereby avoiding common method variance. Our results reveal that personality traits have significantly positive effects on LMX, with impression management behavior also playing a mediating role between them. Interestingly, we also find that group cohesiveness moderates the relationship between impression management behavior and LMX. Our study includes a discussion of the theoretical and practical implications of our findings.