Carboxymethyl Konjac Glucomannan-Chitosan (CKGM-CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions by polyelectrolyte complexation. Investigations of the physicochemical properties of these nanoparticles were undertaken. This study showed that the nanoparticulate system driven by complex formation has potential as an advanced drug-delivery system for water-soluble drugs.