Hydrogel nanoparticles are among the most promising delivery systems for drugs owing to their hydrophilic nature as well as small and easily controllable sizes. Hydrogel nanoparticles demonstrate the features and characteristics of both hydrogels and nanoparticles separately possess at the same time. The pharmacy world will benefit from both the hydrophilicity, versatility, flexibility, high water absorptivity and biocompatibility of these particles and also the advantages of nanoparticles mainly long life span in circulation and also the possibility of being actively or passively targeted to the desired biophase, e.g. tumour sites.