Hospital reorganizations are difficult and often fail to produce their intended benefits. Prior research has investigated how and under which contingencies changes in organizational structure affect the modification of clinician behaviors, yet we know little about how organizational redesign interventions affect physicians' collaborative networks. This paper explores how hospital reorganizations affect physicians' network churn. We developed hypotheses on the relationship between structural characteristics of networks before reorganization and the formation of cross-unit network ties after reorganization. We tested our hypotheses on a sample of 175 physicians in a large teaching hospital. The hospital had recently adopted a new organizational model aimed at enhancing a process-based approach to care delivery. Our findings revealed that the physicians' propensity to form cross-unit ties after the change was related to the structure of their collaborative networks before the change. In particular, the formation of cross-unit relations was negatively related to the size of advice networks before the reorganization. Furthermore, we found that the diversity of network ties along with the presence of structural holes in the physicians' networks before the change moderated this relationship. We discussed the theoretical and practical implications of our findings. In particular, our results may inform organizational redesign interventions within hospitals.