The research presented in this article was aimed at increasing the current understanding of the process of developing Collaborative Improvement (CoI) in Extended Manufacturing Enterprises (EME). Based on action research in three EMEs involving a total of 13 companies from five European countries, the study identifies three different implementation approaches. The bottom-up learning-by-doing approach starts at a practical level, with simple improvement activities, and aims at gradually developing a wide range of CoI knowledge, skills and initiatives. The top-down directive approach starts with aligning the partners' CoI objectives and an assessment of their collaboration and CoI maturity in order to provide a common platform before actually starting improvement activities. The laissez-faire approach builds on shared goals/vision, meetings on equal terms and joint work, in a non-directive and non-facilitated way, though. The article demonstrates how and why the different approaches have different effects on the development of collaborative improvement.