Seven Schiff bases were synthesized from O-carboxymethyl chitosan (CMC) and para-substituted benzaldehydes. The Schiff bases were characterized through Fourier Transform Infrared Spectroscopy, Carbon-13 Nuclear Magnetic Resonance (C-13 NMR), Distortionless Enhancement of Polarization Transfer (DEPT) 135 NMR, elemental analysis, and acid-base titration. Antibacterial activities of the Schiff bases against Escherichia coli (E. coli, ATCC 35218) and Staphylococcus aureus (S. aureus, ATCC 25923) were measured through the optical density method. Antibacterial activity of the Schiff bases differs from the substituent at the para position of benzaldehyde, and decreases as the sequence OCH3 > CH3 > H > F > Cl > Br > NO2. The IC50 of the Schiff base from 4-methoxylbenzylaldehyde against E. coli and S. aureus is 30 and 34 ppm, respectively, much lower than that of chitosan (53, 48 ppm) and CMC (58, 60 ppm).