There is an increasing demand for the natural polymers, composites, and engineering nanomaterials (ENMs) in the water and wastewater treatment (WWT). This is mainly due to the fact that the remediation by above listed materials offer undisputable advantages, such as no generation of pollutants, doesn’t require extra energy inputs, and no high side costs. In this direction, there is much attention on polysaccharides, which are hydrophilic, non-toxic, relatively cheap polymers and possess an inherent variety of functional groups that allow the better interactions of polysaccharides with pollutants. Up ahead, polysaccharides can be obtained easily in the environment by green processes from agricultural wastes, microbial cells etc. Especially, polysaccharide-based nanomaterials (PNMs) show remarkable potential for the removal of different environmental pollutants. There are different kidneys of polysaccharide materials available such as alginate, pectin, gum, cellulose, starch, chitin, and chitosan. However, cost effectiveness, eco-friendly nature, non-toxicity, biodegradability vary from each other. Therefore, the present chapter emphasize on the following issues for the better implications of polysaccharide-based nanomaterials in the remediation of water and wastewater—(i) Characteristics of different polysaccharide materials, (ii) Mechanism of interaction with the pollutants, (iii) Case studies, and (iv) Future perspectives of polysaccharide-based nanomaterials in the remediation. We are of the opinion that this could be a single source of information for the researchers, environmental engineers, academicians and those who are working in the field of sustainable environmental techniques for the restoration of contaminated media.