With a population of over 13 million, Istanbul is one of the biggest city in Europe. The possible increase of population in the future may bring serious problems of water supply after a few decades. Therefore, it is crucial to look for good solutions to problems and potential challenges in water supply and water demand. This paper intended to investigate the currently existing problems in water and wastewater management practices in Istanbul from a supply-demand-reuse perspective; and to look for possible opportunities for a future improvement in order to achieve a sustainable urban water management system in Istanbul by promoting its wastewater management system. In this paper, two interviews of professionals, and a survey in Istanbul city area were conducted for obtaining gather primary data. Analysis of relative literatures is applied for grasping an accurate picture of water and wastewater management in Istanbul. According to the study, authorities are making great efforts to meet the ever increasing demand for water. From a supply-demand-reuse management perspective, Istanbul is still at the stage of supply management with sufficient wastewater treatment. However, there is not much sign of a demand management model, as inadequate effort has been devoted to controlling the increase of water demand. Although reuse management may still be a distant goal for Istanbul to achieve, a good preparation can be started by promoting and further improving the current wastewater management system, as wastewater reuse, if properly managed, will be the best solution that will lead to achieving long-term benefits.