The present investigation was undertaken to assess the Water Quality Index (WQI) of Saroornagar lake, Hyderabad. This 400 year old lake was to provide water for irrigation of farm lands and domestic water purposes. With rapid urbanization in the catchment as well as command areas of the lake and population explosion the lake is heavily polluted recent years, it is essential to assess the quality of water. Samples were collected from four sampling stations for a period of two years and comprehensive physico-chemical analysis was carried out to determine pH, alkalinity, chlorides, DO,BOD, total hardness, calcium, magnesium, nitrates, sulphates and total dissolved solids for evaluating Water Quality Index. The lake quality was calculated from the WQI. The water quality index levels of the lake and all the four stations were manifold higher, indicating water is highly polluted and unsuitable for drinking, domestic and recreational purpose.