Addressing complex and challenging issues entails access to credible systems information in the form of systems maps or diagrams. The purpose of our paper is to describe a participatory action research (PAR) systems mapping activity that was undertaken by an urban informal settlement community in a small Pacific Island Country. A total of 19 households participated in a systems mapping activity to map a household-level water or sanitation system. The individual household systems maps and related data were then used to construct a de-identified aggregated water, sanitation and hygiene (WaSH) marketing systems map (and accompanying narratives) for the informal settlement. We present the marketing systems map, which delineated a series of marketing exchanges, and report on how the map assisted the community to address a number of expressed needs. We conclude by suggesting that systems mapping is a valuable activity that communities could undertake to generate credible systems information to inform and empower collective planning and actions.