This chapter aims to provide a comprehensive review of literature regarding the biomedical applications of modified chitosan nanoparticles. Several examples have been quoted in this connection including; pickering emulsions-chitosan tripolyphosphate nanoparticles in drug delivery system, delivery of salazosulfapyridine which was discovered as sulfa antibiotic in 1930s and has been frequently used to diagnose rheumatoid as well as inflammatory bowel diseases such as ulcerative colitis and Crohn’s disease. Another unique approach has been developed for manufacturing theophylline granules loaded with a polyelectrolyte complex comprising sodium tripolyphosphate and chitosan. Chitosan-5-flurouracil nanoparticles (NPs) have been developed for cancer treatment. Propranolol has been emerged as a non-selective adrenergic antagonist, has also been used to treat cardiovascular illnesses like hypertension, arrhythmia, and angina pectoris. Limited bioavailability (25%) has indeed been found owing to significant first-pass metabolism whereas, nanoparticle-based propranolol techniques have been created to overcome this problem. Desvenlafaxine-loaded PLGA CSNPs has been used as antidepressant. Antipsychotic medicines have also been developed by Quetiapine fumarate loaded chitosan nanoparticles. Stroke is the world’s third most frequent neurological illness, leading to long-term impairment and increased morbidity and death for which Rutin-encapsulated CSNPs have been devised. Herbal therapy has lately been suggested as an alternate technique for developing drugs for a number of neurological illnesses, such as Alzheimer’s disease and epilepsy for the remedy the Piperine-loaded CSNPs have been extensively investigated. For cancer treatment hyaluronic acid-coated CSNPs have been utilized. The Naringenin-loaded sulfobutylether-β-cyclodextrin CSNPs have been associated with permanent vision loss. Apart from these various other chitosan nanoparticles and its derivatives have been utilized including; Spanish Broom (Spartium junceum L.) fiber with vancomycin-loaded CSNPs, Quetiapine fumarate-loaded CSNPs, Rutin-encapsulated CSNPs etc.