ZnO nanoparticles were generated by laser ablation process in liquid media to decorate carbon nanotubes (CNTs) with different amounts of ZnO nanoparticles on their tubular surface in just one step for catalytic degradation against methylene blue dye. The amount of decorated ZnO nanoparticles was controlled by optimizing the laser ablation time. Several techniques were used to investigate the nanocomposite structure as optical, structural, and morphological studies showing that the absorbance characteristic peak showed a difference due to the effect of ZnO/carbon nanotubes interaction. Besides, from X-ray diffraction, it was seen that the diffraction patterns were very closely matched to the crystalline peaks of graphite skeleton and ZnO structure. Moreover, the amount of active sites was increased after decoration to confirm the presence of their interaction. Additionally, it was noted that the amount of coating on CNTs with ZnO was increases as the ablation time increases. This research proved that the existence of CNTs playing a vital role in the composite for the enhancement of the catalytic efficiency compared with pristine ZnO.