Display omitted •Waste cellulose-derived carbon displays high adsorption capacity for MO.•External pore volume plays an important role in MO adsorption.•Equilibrium can be well fitted with both Langmuir and Freundlich isotherms.•Pseudo-2nd-order model predicts kinetics better than the pseudo-1st-order model. High-performance nitrogen-doped porous carbon adsorbents were prepared from waste cellulose fibers using the spray-drying method and used to remove methyl orange (MO) from water. The carbon adsorbents possessed a honeycomb-like turbostratic microstructure with hierarchical pores. Such waste-cellulose-derived carbon adsorbents were found to exhibit a fast adsorption rate towards MO. A sample thermally treated at 800 °C with the highest specific surface area (about 1259.4 m2/g) and total pore volume (about 2.7 cm3/g) exhibited the best MO adsorption capacity (337.8 mg/g), which is significantly higher than that of ZnCl2-activated carbon. The effect of MO initial concentration, pH and temperature on the carbon adsorption was investigated systematically. It was found that the adsorption system is heterogeneous while the isotherm data on the carbon sample can be well described by both Langmuir and Freundlich isotherm models. The high-performance and cost-effective carbon adsorbent described in this paper holds a great promise for dye removal from aqueous solutions.