A novel biobased and highly porous aerogel was fabricated by cross-linking between chitosan (CS) and cellulose nanofibrils (CNFs). The structural and chemical characteristics of the produced CS/CNF aerogel were investigated using several techniques and the adsorption potential of the CS/CNF aerogel was determined by adsorption of acid blue 93 dye (AB93) under different conditions and the isotherm, kinetic, and thermodynamic characteristics of AB93 dye adsorption were analyzed. The investigations showed that the CS/CNF aerogel with a highly connected porous structure and large specific surface area has been successfully fabricated. The isotherm study indicated that the absorption of AB93 with the CS/CNF aerogel obeyed the Langmuir adsorption isotherm with a maximum uptake capacity of 1428.7 (mg g(-1)) at 308 K, which was higher than those reported recently for various absorbents. Overall results of adsorption indicated that the CS/CNF aerogel was a promising material for rapid and efficient adsorption of anionic dyes.