Due to increasing complexity in new product development multi-organization, multi-team (MOMT) projects are becoming more common. They are formed in different industries like computer, automotive, aircraft, and space research. Since many of these projects still fail, more knowledge on the influences on performance in and of such projects is required in order to be able to manage them successfully. The author examines the influences of communication within and between teams on team and project performance, which in turn depends on applied design principles that structure and facilitate that information flow. Quantitative and qualitative analyses reveal that there are differential relations on the team and project level as well as for effectiveness and efficiency. Managerial implications are given of how to structure MOMT projects and the design problem-solving process and thereby facilitate the information flow within and between teams in order to make the teams and projects successful.