The adsorption of reactive blue 4 (RB4) and acid red 183 (AR183) on a multiwall carbon nanotube (MWCNT) was investigated in single and binary dye systems. The MWCNT presented a higher adsorption of RB4 than AR183 in single and binary dye systems, due to stronger interactions. In single dye solutions, adsorption capacities of the MWCNT for RB4 and AR183 at 25 °C are (69 and 45) mg•g -1, respectively. The higher temperature resulted in lower adsorption of the dyes on the MWCNT. In binary dye solutions, RB4 and AR183 showed competitive adsorption, resulting in RB4 adsorption but desorption of AR183 on the MWCNT. RB4 adsorption capacity in binary dye systems was also reduced to 56 mg•g -1 at 25 °C. The interaction of the dyes with MWCNT was found to be dominated by electrostatic attraction.