Aims: Modification of multi-walled carbon nanotubes (MWCNTs) via ozone was carried out to enhance removal benzene from aqueous solutions. Materials and Methods: Multi-walled carbon nanotubes purchased from the Iranian Research Institute of the Petroleum Industry was oxidized by ozone generator at %80 intensity for 5 min and in 30% NaOCl. Results: The Fourier transform infrared analysis showed that the peaks corresponded to the hydroxyl and carboxylic acid groups in modified MWCNTs (MMWCNTs) are more intense than that in non-MMWCNTs. The images of scanning electron microscopy indicated that the MMWCNTs have a lower degree of entanglement with increased porosity compared to the nonmodified one. X-ray diffraction test showed that structural crystallization was increased following the modification. After modification, the efficiency of MWCNTs was increased by 20%. The optimum condition for initial benzene concentration, MWCNT dose, contact time, and pH was: 100 mg/L, 2000 mg/L, 20 min, and 5 respectively. Conclusion: Our research suggested that ozone modification can be a simple method in improvement of the MWCNTs efficiency for removal of benzene from aqueous solution.