Water is the most important commodity for us all in different fields. Water makes our planet unique, and superior compared to other planets. There are several areas where we have resources of water, but due to recent environmental conditions water is going to become contaminated by the presence of lots of harmful chemicals. It is necessary in the present era to decrease pollutants in water, not least for the healthy life of the next generation. Nowadays nanomaterials are applied for the removal of different pollutants in wastewater. The size of nanomaterial in between 1 to 100 nm, when nanomaterials change from macro to nano size it shows drastic differences in their appearance, toughness, conductivity, and sensitivity also nanomaterials show good catalytic activities, high reactivity, and better adsorption ability, also nanoparticles that have a very small size and bigger surface area show many applications in different fields. The nano-size materials enhanced the catalytic activities and adsorption capacity of nanomaterials as compared to bulk materials, due to their small size and large surface area it has been shown that nano catalysts and adsorption power of nano-size materials can expand the oxidation ability towards pollutants from wastewater effectively. The different mechanism works for the removal of pollutants from wastewater like Oxidative neutralization, Adhesive detoxification, Adsorption to active carbon, Photocatalytic degradation, etc. In this chapter we provide an overview of the basic mechanisms of adsorption and catalytic processes of nanomaterials and gradually we discuss the role of nanomaterials in pollutant removal and degradation and finally discuss the interaction mechanism between nanomaterials and pollutant in the waste water.