The provision of sustainable water, sanitation and hygiene (WaSH) services is essential for human health and development. In order to achieve this sustainability, reliable data is needed to support planning, and improved prioritisation tools are required to evaluate sector performance and promote decision-making. In this context, the present paper introduces to the WaSH sector the ELECTRE-III model, which has proved successful for multi-criteria ranking in water resources management. This article presents 1,600 communities in Nicaragua as case study and evaluates the method’s suitability to rank the performance of a large number of communities on multiple criteria. Results indicate that ELECTRE-III is effective at assessing communities at a large-scale and targeting the neediest areas for WaSH improvements.