<p>This review extensively evaluates recent advances in chitosan-based nanocomposites for environmental remediation and sensing applications. The scope covers synthesis methodologies, structural modifications, and performance evaluation of chitosan nanocomposites in two primary application domains: adsorption-based water treatment and electrochemical sensing. This review highlights trends in the development of nanocomposites, focusing on the incorporation of metallic nanoparticles, graphene-based materials and conductive polymers to improve the properties of chitosan. It also evaluates the adsorption mechanisms, kinetic models, and electrochemical sensing principles that influences material performance. The results reported in the literature indicate that chitosan–graphene oxide composites achieve high adsorption capacities, whereas chitosan–metal oxide nanocomposites exhibit improved electrochemical sensitivity with detection limits in the nanomolar range.</p> Graphical Abstract <p></p>