Nanoscaled MoO₃ particles loaded on ZnO nanorods (ZnO NRs) were synthesized via a hydrothermal-precipitation method. X-ray diffraction, field emission-scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, UV–vis absorption and photoluminescence studies were used to characterize the structures, morphologies and optical properties of the composites. The results showed that pure orthorhombic phase of α-MoO₃ nanoparticles with average sizes of 15–21nm were well dispersed on the surface of ZnO NRs. The MoO₃/ZnO NR composites also showed high charge separation efficiency and ·OH generation ability as evidenced by their photoluminescence spectra. The photocatalytic studies revealed that the MoO₃/ZnO NRs showed superior visible-light degradation rate for herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) compared with the pure ZnO NRs. Such enhancement might be attributed to the high separation efficiency of photogenerated electron–hole pairs based on the cooperative roles between bi-components of MoO₃ and ZnO NRs. The photocatalytic studies also showed that various parameters such as the MoO₃ content in the composite, MoO₃/ZnO NRs amount, initial 2,4-D concentration and solution pH exerted their individual influence on the 2,4-D degradation. Moreover, the MoO₃/ZnO NRs could be easily recovered and reused due to their one-dimensional nanostructural property.