Abstract Multi-stakeholder engagement is critical for making progress towards Sustainable Development Goal (SDG) 6 ‘Ensure access to water and sanitation for all’, which is currently off track to be achieved by 2030. The aim of this paper was to investigate mutual accountability and multi-stakeholder platforms in the WASH sector in a diverse range of countries. Data were collected by Sanitation and Water for All (SWA) Research and Learning Constituency partners and collaborators in five SWA member countries: Bangladesh, Indonesia, Kenya, Peru and Somalia. Data collection involved document review, key informant interviews and workshops, and an online questionnaire. Across all the case study countries, there were no clear examples of mutual accountability mechanisms being widely used in the WASH sector. However, the findings indicate that some of the case study countries have active WASH multi-stakeholder platforms involving a range of actors from government, civil society and the private sector; however, these typically function as coordination and communication platforms rather than supporting mutual accountability. Other case study countries did not have multi-stakeholder platforms involving a diverse range of actors, and instead had platforms established for single stakeholder groups such as the private sector or civil society, leaving certain groups out of activities. Overall, the study highlights the importance of establishing strong multi-stakeholder processes and platforms that bring together a range of actors including government, civil society, private sector, research actors, and WASH external support organizations. Such platforms could provide a foundation to enable mutual accountability between these actors by providing a space to set commitments and monitor progress and have potential to strengthen WASH systems both nationally and globally.