This study aims to investigate the effect of catalysts on the preparation of carbon nanotubes (CNTs) and the catalytic properties of Co/CNT for toluene oxidation between 175 and 250 degrees C. A different ratio of Co to Mo supported on Al2O3 was used in the chemical vapor deposition method to synthesize the carbon nanotubes. Moreover, the catalytic activities of Al2O3-supported catalysts for toluene oxidation were also measured, and the results were compared with the catalytic activities of Co/CNT catalysts. To confirm the characterization of CNT and Co/CNT, the composition and morphology of various catalysts were analyzed by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectra, BET, and X-ray photoelectron spectroscopy (XPS). The results indicated that the catalytic activity of Co/CNT catalysts was higher than that of the Al2O3-supported catalysts. Furthermore, the catalytic activity of Co/CNT prepared by using 2.4% Co-0.6% Mo/Al2O3 for toluene oxidation was 100% at 225 degrees C. The results demonstrated that the removal efficiency of toluene depends on the species of catalysts synthesized on the carbon nanotubes.