<p>Peri-urban settlements are characterized by inadequate wastewater management. Decentralized wastewater management systems are promising alternatives for reducing pollution from untreated sewage entering receiving water bodies, but the social, economic, and environmental conditions in peri-urban settlements require careful technology selection to ensure sustainability. Several domestic wastewater technology selection tools exist; however, these are typically designed for either urban or rural contexts. For this reason, this work proposes a decentralized wastewater technology selection tool for the context of peri-urban settlements that includes participation of local stakeholders in decision-making. The tool includes a technical component with three stages that involve multicriteria methods based on the Analytical Hierarchy Process and Montecarlo simulation to reduce uncertainty: i) decision according to context (settlement population, settlement typology, energy availability); ii) superior decision levels (nine sub-criteria from technical, environmental and economic dimensions); iii) technical and economic feasibility (dimensioning; cost of investment, operation and maintenance; availability to pay). The tool proposes a social strategy throughout the entire process to ensure stakeholder participation, aiming to strengthen capacities and knowledge co-production for informed technology selection. The tool was validated in a peri-urban settlement of Bucaramanga (Colombia), showing robustness and soundness. This innovative approach contributes to the search for sustainable solutions by facilitating the use of systematic tools by technicians and professionals in these contexts.</p>