Purpose ‐ Members' knowledge is the most important resource in NGOs and it is important to stimulate its exchange. Knowledge that is needed to act in complex situations is hard to exchange, but Web 2.0 technologies provide a toolbox to develop a knowledge management strategy. The paper aims to specify optimal conditions and necessary measures that NGOs should take in order to successfully use Web 2.0 technologies for knowledge exchange.Design/methodology/approach ‐ NGOs and Web 2.0 technologies have specific characteristics in common. It is suggested that these characteristics require certain prerequisites in order to make the use of Web 2.0 technologies successful. Using an iterative and participative design method, a case study is presented that investigated prior boundary conditions and implemented a Web 2.0-based platform as knowledge management strategy in a large NGO.Findings ‐ NGOs and Web 2.0 are based on strong voluntariness, they are democratic, contribution and personality are strongly tied to each other, and education is rarely formal. Therefore, there is a strong need for contact between members, internal motivation and organizational identification, for quality criteria, for protected spaces and pattern-structures, if Web 2.0 technologies shall lead to successful knowledge management. The case study demonstrates that considering these circumstances enabled the successful implementation in a large NGO.Practical implications ‐ The current research helps NGOs to successfully implement Web 2.0 technologies as a means to support knowledge management. A figure with the crucial questions and the means that have to be taken in dependence of the answers is provided.Originality/value ‐ NGOs do not have the same means to develop formal management strategies as other organizations. Therefore, a thorough understanding of the circumstances that enable knowledge exchange with Web 2.0 technologies is needed. The current research provides information about optimal circumstances and about possibilities to improve less promising circumstances.