Access to safe water is considered a minimal necessity for human life. Due to the global scarcity of water, it has become essential to treat and purify wastewater for its use in domestic, industrial, and agricultural fields. In order to improve the quality of water, many conventional methods of water purification are being employed worldwide, which have proven inadequate to deal with the current scenario of water pollution levels and types. Hence researchers are in a race to develop novel, cost-effective, and sustainable procedures to remove newly emerging water contaminants. Of these novel procedures, carbohydrate polymer-based nanocomposites are grabbing attention globally. A nanocomposite is a hybrid material showing significant changes in properties to its bulk counterpart. This chapter will highlight the practical functionality of polymer-based nanocomposites in water purification technologies and their scope in sustainable technology development and superiority compared to conventional technologies. The various approaches to synthesizing carbohydrate polymer-based nanocomposites are discussed while detailing their mechanisms of contaminant removal and non-hazardous applications in water pollution management. The challenges and opportunities for applying these nano adsorbents in practical applications have also been highlighted in this chapter.