Rapid industrialization and population boom have led to deterioration of water quality, rising health issues and environmental damage, which made it imperative to monitor and regulate the water pollutants. Earlier, water samples were monitored using grab sampling method and then analysis was performed in the laboratory. This process is arduous and time consuming; also, there are poor chances of detecting a periodic pollution. For a proactive response sensor technology is popular these days for pollutant monitoring. A variety of sensing techniques and materials are available. But recently nanomaterials have absorbed attention for fabricating sensors owing to their high surface to volume ratio, ease of functionalization which enable them to have high specificity and sensitivity. This chapter intends to review the emerging materials used for making water pollutant sensors and gives an insight into the emerging techniques like microfluidic sensors, biosensors, wireless sensor network and smart sensors.