Actors join collaboration to complement and strengthen their existing capacity, broadly defined. However, they must first invest their capacity to build collaboration until it is fully developed and produces intended outcomes. This creates a challenge of ongoing work versus deferred gains, which is identified as “capacity tension” in this study. To advance theory and practice on the processes of managing capacity tension and sustaining collaboration, this study examines a nonprofit collaboration that struggled with constant capacity tensions yet persisted for several years with some meaningful achievements. Drawing on a unique longitudinal data from 165 interviews with 27 collaboration participants over 11 rounds of interviews, participant-observations, and archival documents between 2016 and 2020, this study reveals the presence of ongoing capacity tension in collaboration and offers various coping strategies. Based on the analysis, a process model on navigating capacity tension in collaboration is proposed.