Herein, a sodium alginate/poly (acrylic acid)/oxidized-multi-walled carbon nanotubes hydrogel nanocomposite (SA/p(AAc)/o-MWCNTs HNC) was synthesized by in situ free-radical polymerization method. The synthesized SA/p(AAc)/o-MWCNTs HNC was used to remove methylene blue (MB) from aqueous solution. The synthesized HNC was confirmed by employing various characterization techniques. The SA/p(AAc)/o-MWCNTs HNC exhibited a maximum swelling capacity of 2265.4% at pH 8.0. The influence of vital parameters in the sorption process including the initial pH, adsorption dose, contact time and concentration were systematically examined on a batch mode. Subsequently, adsorption kinetics as well as isotherm models were applied to assess the nature and mechanism of the adsorption process. Adsorption kinetics were best described by pseudo-second-order model, while the Langmuir isotherm model governed the adsorption isotherm. The SA/p(AAc)/o-MWCNTs HNC exhibited a maximum adsorption capacity of 1596.0 mg/g at 25°C. This adsorbent showed excellent MB uptake and good regeneration ability.