Timah Tasoh Lake is surrounded by various types of land use activities ranging from industrial, agricultural and quarrying activities. These activities will affect the water quality and a threat to the ecosystem of the lake. A study was conducted in Timah Tasoh catchment areas with the aim to investigate the water quality parameters such as physical, chemical and biological in the Timah Tasoh Lake. The water quality study involved in-situ measurement and laboratory analysis. National Water Quality Standard (NWQS) for Malaysia was applied. The study concludes that the water quality was varied between stations and tends to decrease from upstream towards the lake (downstream).