In this study, chitosan-catechin conjugates were prepared by free radical-mediated grafting mechanism using different molar ratios of chitosan residue and catechin. The chitosan-catechin conjugates were verified using 1 H NMR and differential scanning calorimetry, and catechin content in the chitosan-catechin conjugates was determined. Catechin content was increased with increasing molar ratio; however, grafting efficiency was decreased with increasing molar ratio. Antioxidant abilities of the chitosan-catechin conjugates were investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide, and 2-azinobis( 3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) cation radical scavenging assay, and reducing power. All the chitosancatechin conjugates showed increased antioxidant abilities compared to the unmodified chitosan (p < 0.05), and the chitosancatechin (III), which was prepared using 1:1 of molar ratio, showed the highest antioxidant activities. In addition, the chitosancatechin conjugates significantly (p < 0.05) inhibited the formation of malondialdehyde, which is an indicator of lipid peroxidation, in linoleic acid emulsion system.