Despite a growing interest in the phenomenon of open innovation (OI), empirical evidence documenting the link between new product development capabilities, OI practices, and new product innovativeness is scarce. Eminent scholars have called for large-scale studies that systematically investigate the OI paradigm. Drawing on the knowledge-based view of the firm, new product development, and NPD capabilities literature streams, we conceptualize a framework in which OI practices are disentangled according to the stage of the new product development process in which they occur (development stage or commercialization stage). We identify two major types of OI practices: development-centric OI (which occurs in the development stage) and commercialization-centric OI (which occurs in the commercialization stage). Specific types of NPD capabilities R&D, market information management, and launch are expected to both influence the extent to which each OI practice is implemented and moderate the effect of each OI practice on product portfolio innovativeness and firm performance. The empirical analysis combines primary data from a survey of 239 firms with secondary data on innovation and financial outcomes. Our results support our hypotheses and indicate a need to differentiate among the different kinds of OI practices while elaborating on the complex role played by NPD capabilities in influencing OI practices.