Water pollution by various toxic contaminants has become one of the most serious problems worldwide. Various technologies have been used to treat water and waste water including chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation–flocculation, flotation and electrochemical methods. From past few decades, nanotechnology has gained wide attention and various nanomaterials have been developed for the water remediation. In the present review article, various nanomaterials have been reviewed which have been used for water decontamination. The special emphasis in the review has been given on adsorption, photocatalytic and antibacterial activity of nanomaterials.