Multiteam structures are increasingly used to coordinate complex tasks between different groups. To realize this potential, however, the members of a multiteam structure must manage a complex set of boundary relations within, between, and beyond the various constituent teams—boundary relations that can be cooperative, competitive, or some combination of both at the same time. This multimethod study provides insight into how multiteam structures can meet this challenge. Specifically, we examined how the different organizations that utilize and support the Dutch railway system learned to manage boundaries as they transitioned from a centralized, arms-length structure to a colocated, multiteam structure for coordinating disruption responses (i.e., the Rail Operations Control Center (ROCC)). In part 1 of our study, qualitative analyses of interview, observational, and archival data suggested that learning to manage boundaries within the ROCC was not simple or linear but evolved through trial and error during various phases. Ultimately, the ROCC developed an approach we call “integrated pluralism,” establishing a dynamic balance that combines both collaborative and competitive approaches to boundary management. In this manner, the ROCC teams were able to attain integrated solutions and coordinated task accomplishment while simultaneously defending internal team operations and home organization interests. In part 2, we employed an interrupted time series analysis to demonstrate that the implementation of the ROCC resulted in significant performance improvements. Consistent with the results of part 1, we found that these improvements emerged gradually over time as teams learned to work out their boundary relations and transitioned to integrated pluralism. These findings provide new insights into how individuals and teams can work together to tackle the unique boundary management challenges presented by multiteam structures and illuminate the dynamic trial and error process by which component teams can learn to both cooperate and compete.