We argue that leader-member exchange (LMX) standing relative to the LMX relationships of other coworkers (RLMX) in workgroups may influence employees' job performance. Based on social comparison and social identity theories, we develop a moderated-mediation model of the psychological processes linking RLMX and job performance, and test it on a sample of 252 employees and 42 managers working in two large banks. Results of hierarchical regression analyses provide support for the model. We found that RLMX was positively related to social identification after controlling for perceptions of LMX; and also that social identification mediated the relationship between RLMX and job performance. We found further that negative affectivity moderated the relationship between RLMX and social identification which, in turn,also mediated the interactive effect on job performance.