Performance in new product development projects influences companies’ success and competitiveness. Co-development is one possible pathway for companies to develop new products effectively in cooperation with their customers. However, there are multiple factors affecting the outcomes of such cooperations. In this research, we develop a new and comprehensive conceptual framework that explains success of co-development projects in B2B. As part of this framework we integrate multiple relevant underlying mechanisms. In particular, organizational design, cultural aspects, power structures within the project team, and how co-development is framed within companies are key drivers because of their high relevance for the success of co-development projects. This conceptual work contributes a conceptual foundation for further empirical research within the co-development area and has interesting implications for managerial practice. In line with this endeavor, the framework serves as basis for an ongoing data collection, which considers supplier project managers, supplier team members, and customers.