Irrigation has been found to be a central key part in curbing food scarcity not only in Tanzania but also in many other developing countries. The continued dependence on rainfall in agriculture has proved incapable of sustaining the population increase. This study examines the sustainability of smallholder irrigated agriculture as a means of improving social and economic benefits in the Mbarali district, located in Usangu plains of South-West Tanzania. Specifically the study focuses on: The existing national policies and their roles in irrigation development; Characteristics of the existing irrigation systems and their roles towards poverty alleviation; Productivity of irrigation schemes and profit margins for poverty alleviation; Rural livelihoods strategies towards poverty alleviation;and arrangements of local institutions towards sustainable irrigation. The study is confined to smallholder irrigation schemes in the Igurusi ward. The selected villages for the in-depth study were Majenje, Igurusi, Chamoto, Uhambule and Mahango.