Chitin and chitosan are natural biopolymers derived from crustacean shells, fungi and insects and have emerged as versatile materials for therapeutic applications due to their biodegradability, biocompatibility and non-toxic nature. These polysaccharides, their derivatives and nanocomposites offer significant potential to address global health challenges sustainably. The functional modifications of chitin and chitosan enhance their physicochemical properties and enable their utilization in therapeutics. Chitosan-based nanocomposites often functionalized with metallic or polymeric nanoparticles, provide improved bioavailability and targeted therapeutic efficacy for various diseases, including cancer and microbial infections. Their antimicrobial, anti-inflammatory and antioxidant properties have also made them invaluable in wound care management, promoting faster healing and reducing scarring. Emerging therapeutic and medical applications include bioactive scaffolds for tissue regeneration and carriers for genetic material in gene therapy. The eco-friendly production methods and abundant availability of raw materials underline their sustainability and global applicability. This chapter emphasizes recent advancements in the multifunctional applications of chitin, chitosan, its derivatives and nanocomposites. It highlights their pivotal role in sustainable therapeutic interventions and the promise they hold for next-generation biomedical solutions.