In this study, glutaraldehyde–chitosan complexes (GA–chitosan) were prepared and were used as functional additives to enhance the strength properties of cellulose fiber networks. The adsorption and distribution of GA–chitosan on the surface of cellulose fiber were characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry. The effects of glutaraldehyde dosage and GA–chitosan to fiber ratio on the strength properties, including wet‐strength, wet‐web strength, and dry strength, were investigated. GA–chitosan did not require high temperature curing and had good cross‐linking rates at room temperature. Samples treated with GA–chitosan exhibited significant improvements in their mechanical properties. Wet tensile index and wet‐web tensile index (both at 50% solids), and dry tensile index, were increased by about 1300, 190, and 115%, respectively. The GA–chitosan additive developed in this study provides a useful approach to prepare high‐performance value‐added specialty wood‐fiber based products. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42375.