Increasing product variety, rapid new product introductions, volatile market demands, and pressure for cost reductions are among the main drivers for developing changeable and reconfigurable manufacturing systems constituting platforms that can be developed and utilized jointly with product platforms. However, methodologies to support platform-based co-development of products and manufacturing systems remain limited in previous research, including lack of knowledge on successful practices for the platform-based co-development project and process. Therefore, the objective of the research presented in this paper is to identify practices for platform-based co-development of products and manufacturing systems through a case study of a company that has successfully transitioned towards changeability through platform-based co-development. The findings cover various aspects of the co-development process and project, providing initial insight into how to enable joint development of products and manufacturing systems, in order to achieve changeability and reconfigurability.