The main objective of this study was to ascertain the impact of public participation on the sustainability of water projects in the Makueni sub-county. Evaluating the effects of participatory management, planning, and monitoring on the sustainability of water projects in Makueni Sub County-Makueni County was the specific aim of the study. Theoretically, sustainability theory and community participation theory underpinned the research. Target population 34,352 households, 117 members of the Project Management Committee, and 15 county officers are the study's target population. Asample size of 380wasselected using simple random sampling.The 15 technical officers were selected using a census, yielding a sample size of 395 in total. For the goal of triangulating data, both quantitative and qualitative data for the studywascollected using a structured questionnaire,which employeda descriptive research design. Using SPSS version 23, descriptive analysis of the collected data wasperformed before being shown as graphs and frequency tables. To describe the link between the variables, a multiple regression model wasemployed.The regression analysis demonstrates that participatory planning has a strong and positive effect on the sustainability of water projects in Makueni Sub County. It shows that as the level of community involvement in planning activities increases, the sustainability of these projects improves significantly. Similarly, participatory management positively influences sustainability, indicating that engaging local communities in the management and decision-making processes of water projects contributes to their long-term success.Additionally, the analysis highlights that participatory monitoring is associated with better sustainability outcomes. The study recommends that increased community involvement in monitoring and evaluation activities helps identify and address issues promptly, thereby enhancing the overall effectiveness and durability of water projects