Water safety is a global health goal and the water borne diseases are a major crisis on health. Therefore, detection of microbial pathogens and different contaminants in water is the solution to the prevention and recognition of problems related to health and safety. Biosensors are being widely used for the detection of various contaminants in water. A biosensor is a self-contained integrated device capable of providing specific quantitative analytical information using a biological-recognition element, which is retained in direct contact with a transduction element. This paper summarizes recent advances made in detection and quantification of waterborne contaminants with different types of biosensors that offers capabilities for rapid, miniaturized on-line and in-situ analysis with minimal waste production. © 2010.