Theory and research note the ubiquity of multiplex workplace friendships—multifaceted relationships that superimpose friendship with work‐focused interactions—but it is unclear how they compel or hinder job performance. In a study of insurance company employees (n = 168), we found that the number of multiplex workplace friendships in one's social network is positively associated with supervisor ratings of job performance. However, we also found that there is a negative indirect effect on job performance through emotional exhaustion, which is offset, in part, through enhanced positive affect. Results of a second study of restaurant and retail sales employees (n = 182) provide greater insight into the positive and negative effects of multiplex workplace friendships. Specifically, these relationships enhanced job performance through trust but detracted from job performance through maintenance difficulty. Collectively, our results illustrate that having a large number of multiplex friendships at work is a mixed blessing. Although the provision and restoration of resources fostered by multiplex relationships benefits employee job performance, these benefits are muted somewhat by the personal resources they deplete.