This paper examines knowledge integration processes that take place between suppliers and their customers, with a specific focus on how suppliers integrate the knowledge of their customers in their new solution development processes. Five customer collaborations in a four-solution development process at one Swedish and one Finnish international supplier are studied. The findings indicate that knowledge integration between supplier and customer in the ideation, development and commercialization phase of the solution development process is not performed uniformly. In fact, evidence suggests that the knowledge integrating intensity and the content of knowledge might change throughout the solution development process. The paper’s contribution to the managerial practice lies in the findings that can help suppliers manage their expectations regarding the knowledge that they could attain in each phase of the solution development process.