In interorganizational research and development (R&D) teams, diverse skills and insights may be combined productively, but the team members' differing organizational backgrounds may also inhibit team performance. In this paper, it is argued that interorganizational R&D teams are more likely to perform with a certain demographic composition. In particular, the problems of an organizational divide can be overcome by a second, demographic divide that cuts across organizational boundaries. With a cross‐cutting demographic divide – or faultline – interorganizational R&D teams may perform; without it, they tend to perform poorly. Supportive evidence is provided in a fuzzy‐set qualitative comparative analysis on 51 projects conducted in a single R&D partnership. As this implies, interorganizational R&D teams should deliberately be composed to show a cross‐cutting demographic divide.