Since 2002, the Madagascar Diorano-WASH Coalition has operated in an environment where only 38% of the population has access to safe water and only 52% of houses are equipped with latrines. Unsurprisingly, with this backdrop, diarrhoea has been identified as the second highest cause of death among children. In this case study, part of the series examining individual countries, we look at the building of the successful Diorano-WASH Coalition, showcasing the evolution, activities and impact made in recent years. WASH Coalitions are involved in activities ranging from participating in information sharing to advocating specific policy changes and everything in between. All, though, have in common a commitment to addressing the need for improved systematic communication, collaboration, and joint action among sector stakeholders in their country of operation. Each WASH Coalition must tailor its approach to suit the country it operates in to achieve the greatest benefits. Here, we look at the two significant factors that contributed to the clear success in Madagascar.Le WSSCC présente le travail des coalitions WASH dans une série d’études de cas des pays de ces coalitions. Les dites études présentent l’évolution, les activités et l’impact des coalitions nationales WASH. Cette édition se concentre sur le pays de Madagascar, où la coalition Diorano-WASH est devenue le principal corps sectoriel de coordination afin d’assurer sensibilisation et mobilisation relatives à l’hygiène et l’assainissement.