The United Nations Millennium Declaration and resolutions at the 2002 World Summit on Sustainable Development give high priority to poverty reduction in international development agenda for the next decade and a half. It is now widely recognized that water resources development and management play a fundamental role in sustainable growth and poverty reduction. However, investments in water resources development, which were considered a high priority by governments and aid agencies for decades, have fallen drastically. The key question addressed in this paper is: Can water resources development reduce poverty? It examines the impacts of past investments on water resources development and management, (especially on irrigation), on poverty reduction. It is shown that past investments in irrigation development have made a significant contribution to alleviating poverty. In recent years investments made by private farmers in groundwater irrigation may have had a larger impact on livelihoods for poor people than the public investments in large-scale surface water irrigation systems. It is argued that there is not a single silver bullet to reduce poverty though water resources development or management. The best chance for lasting and sustainable impact on poverty is likely to be achieved through a combination of sustainable water resources development, combined with the development of appropriate pro-poor institutions and technologies.