An efficient five-step synthetic route was developed for full N-substitution of chitosan with a quaternary betaine moiety. The developed synthetic procedure can also be controlled to produce chitosan N-betainates having lesser degrees of substitution. 6-O-Triphenylmethylchitosan, which is highly soluble in organic solvents, was used as an intermediate for N-acylation reactions. Intermediate products were characterized by C-13 CP/MAS NMR, FT-IR, and elemental analysis. The water-soluble quaternary chitosan N-betainates were thoroughly characterized by H-1 NMR and C-13 NMR and by 2D H-1-H-1 COSY NMR and H-13-H-1 HSQC NMR. Degrees of substitution were determined from the H-1 NMR spectra. A significant degradation of the polysaccharide backbone during the synthetic procedure was determined by GPC with a light scattering detector.