Chitosan (CS) is one of the most successfully developed biodegradable polymers. Among the numerous polymers developed to formulate polymeric nanoparticles, CS has fascinated considerable attention due to its appealing properties: (i) biodegradability and biocompatibility, (ii) FDA approval for wound dressings as well as in dietary application, (iii) non-toxicity, (v) scope of sustained release, (vi) probability to modify surface properties and (vii) scope of target nanoparticles (NPs) to particular organs or cells. This review presents different preparation methods of chitosan nanoparticles (CSNPs) from the methodological and mechanistic point of view. The crosslinking agent including aldehyde, tripolyphosphate (TPP), genipin and other cross linkers and the physicochemical behaviour of CSNPs including drug loading, drug release, particles size, zeta-potential and stability are briefly discussed. This review also presents why CS has been chosen to design nanoparticles (NPs) as drug delivery systems in various pharmaceutical applications. Display omitted