This paper introduces the notion of "temporal boundary spanning" and highlights the key role of project management in resolving temporal tensions among partners participating in interorganizational projects (IOPs). The present study, which is based on data from 93 IOPs undertaken within a major change program, relies on in-depth, semi-structured interviews, observations, and detailed analyses of written documents and procedures from those IOPs. Based on the data, we inductively develop a practice-based theory that identifies three main practices (framing, synchronizing, hyping) used to resolve the central temporal tensions observed in the studied IOPs. In that respect, the paper offers novel insights into the role and practice of project management in IOPs. (C) 2018 Elsevier Ltd, APM and IPMA. All rights reserved.