Abstract Purpose -Many manufacturing firms source components and subsystems from suppliers. Consequently, the suppliers' product and manufacturing knowledge is a central concern at the interface between R&D and manufacturing. This paper specifically investigates how supplier knowledge is integrated and what role trust plays in knowledge integration with suppliers at the R&D -manufacturing interface. Design/methodology/approach -The study is based on qualitative case studies of two different collaborations with suppliers at one firm. Findings -Two distinct processes are identified. First, capturing represents knowledge integration through decoupling, for which a basic level of trust specifically with regard to the competence of the supplier is necessary. Capturing can take place through interactions that are limited in time and scope. Second, joint learning represents a coupled knowledge integration process and takes place during a more extended period of time preceding and following the R&D-manufacturing interface and builds on relational-based trust. Practical implications -The interface between R&D and manufacturing needs to be extended to include a focus on suppliers' contributions in terms of product and manufacturing knowledge. The choice for suitable knowledge integration processes needs to be guided by concerns about the level of trust and the character of the supplier contributions. Originality/value -The paper adds new insights to previous literature by distinguishing between different types of knowledge integration processes and levels of trust. It bridges the gap between innovation and operations management, and clearly shows that the interface between R&D and manufacturing crosses organizational borders. Key words Knowledge integration; Buyer-Supplier collaboration; Trust; Product development; R&D-manufacturing interface 2 Introduction Suppliers are increasingly contributing to their buyer's product development processes and acting as production partners (e.g., Increased levels of knowledge integration between buyers and suppliers can help improve products and processes, decision making, and the problem resolution of product development and manufacturing by taking advantage of suppliers' product technology and manufacturing expertise The paper is structured as follows: First a theoretical framework related to the subject of knowledge integration and trust in product development collaborations is provided. Then, the methodology chosen for the study is presented. The paper proceeds with a presentation of the findings which is followed by an analysis of the data. Finally, there is a conclusion where managerial implications and suggestions for further research are presented