The preparation of guar gum nanoparticles by nanoprecipitation and cross-linking method is reported here. Nanoparticles act as potential carries for several classes of drugs and cosmetics. It has been found that the formation of nanoparticles depends upon the molecular mass of the galactomannan, solvent, surfactant, cross-linker and agitation. The galactomannan nanoparticles functionalized with lipase and crystal violet as model drugs were used for release study. The sizes of the particles in suspension have been measured by light scattering technique. The size and the morphology of the particles have been determined by electron microscopy studies. Optimized method produced spherical nanoparticles of size ∼20–50 nm with a polydispersity index in the range 0.1–0.4.