Management scholars have rarely analyzed how prior social networks might help or hinder the job performance of new organizational members. However, internal and external job markets are increasingly characterized by high mobility of experienced professionals, who have extensive social networks rooted in their past collaborations and shared work experiences. Organizations rely more frequently on project teams and project-based organizing to perform interdependent tasks, so employees transition more often across project teams - and firms - in their boundary-less careers. These changes call for a better understanding of whether the reactivation of past social ties is likely to help or hinder the job performance of new employees, especially those engaged in highly interdependent tasks. The object of this study is to theorize and empirically test the mechanisms by which the reactivation of a particular social tie - shared work experience - may impact new members' performance. Using a social networks lens to study new members' organizational entries, this study not only contributes to the recent fast-growing literature on the reactivation of social ties, but also to studies on new members' performance, and has considerable relevance for enhancing an organization's performance through the better management of its expert workers' human and social capital.