Dissertation (MSc Natural Resources Management)The study analyzed the effectiveness of the Community Owned Water Supply Organization (COWSO's) management in sustainability of Rural Water Project in Kilombero District. Specifically the study aimed to examine how the COWSO managed the RWP and analyzes their sustainability on post construction stage. The study adopted a cross sectional study design where by a total of 6 projects were surveyed across the study area and 34 users and 12 key informants were interviewed. In addition 2 FGD were conducted to triangulate the collected information. The collected data were then processed and analyzed by using SPSS 21 version. The study findings show that COWSO management model exists mostly on the newly constructed projects in the study area and the community started to know the role and responsibilities of them and the COWSO resulted to the stable water services for the surveyed projects within the study area due to capability of managing O & M cost. The study found that the operators of the projects are neither employed nor capable and are low paid which can hinder the life span of the RWP. Through study findings it has been seen that for sustainable management of RWP the Government of Tanzania should take immediate action though policy changes and start to standardize qualification of operators and subsidizes payment of operator‟s salary and some of the O & M cost rather than leaving full operation to COWSO. Finally the study concluded that COWSO management cannot brings the sustainability without other factors like community awareness and sensitization though local training and education, participatory and openness and continuous government support in both aspects of technical and financial because rural community needs safe and clean water for their daily life and future development.