In this work, the biochar adsorbent carboxymethyl cellulose (CMC), was prepared from the pyrolysis (600 °C, 120 min) of chicken manure for the removal of methyl orange (MO) from aqueous solution, and its physicochemical properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). The experimental parameters including agitation speed, initial solution pH, biochar dosage and contact time on the adsorption properties of MO from aqueous solution onto CMC were investigated in batch experiments. The kinetic adsorption of different initial concentration could be accurately described by the pseudo-second-order model and the overall rate process was apparently influenced by external mass transfer and intra-particle diffusion. Furthermore, the Langmuir isotherm model showed a better fit with equilibrium data (R2 > 0.99), with the maximum adsorption capacity of 39.47 mg·g−1 at 25 °C. Moreover, the thermodynamic parameters indicated that the adsorption of MO onto CMC was a spontaneous and endothermic process. The results of this study indicated that CMC could be used as a promising biomass adsorbent material for aqueous solutions containing MO.