A novel cellulose-based aerogel was prepared by a chemical cross-linking reaction and hydrogen bonding between cellulose nanofibers (CNF), polyethylene glycol diglycidyl ether (PEGDE), and hyperbranched polyethyleneimine (HPEI). The obtained aerogel was employed as an adsorbent for the removal of Congo red (CR) dye. The aerogel morphology was examined by scanning electron microscopy (SEM), the chemical structure and thermal stability of aerogels were characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), and the thermal stability was determined using thermogravimetric analysis (TGA). The influences of contact time, pH value, concentration of dyes, and adsorptive selectivity on the adsorption capacity of the aerogels were investigated. The adsorption experiment showed that the aerogels were excellent adsorbents of CR due to their highly porous structure and the existence of abundant amine groups. Thermodynamic and kinetic studies showed that a pseudo-second-order equation (R² > 0.9967) and Langmuir model (R² > 0.9948) were more suitable for the adsorption of the aerogel. The maximum adsorption capacity for CR by the aerogel according to the Langmuir model was 2125.96 mg g⁻¹.