Magnetic carbon nanotube (mCNT) was formed via direct mixing of carbon nanotube (CNT) with magnetic nanoparticle (MNP) in dye solution. When the mass ratio of MNP to CNT was 4:1, all CNT were magnetically collected. The adsorption performance of mCNT was evaluated using methyl blue (MB) as a model adsorbate. Equilibrium of MB adsorption was attained in 60 min, and maximum adsorption occurred at pH 3–6. MB adsorption was independent of ionic strength and followed pseudo-second-order kinetics. According to the Langmuir isotherm, adsorption capacity of mCNT for MB was 115.34 mg g−1. Thermodynamic analysis suggested MB adsorption onto mCNT was a spontaneous process. Reusability study results showed that 97.06, 96.26, 94.33, 92.91 and 90.14% of MB were removed in five consecutive cycles. The study suggests that the mCNT has a great potential application in dye removal from industrial wastewater.