TiO2 nanotube array (TiO2 NT) was co-decorated by reduced graphene oxide (RGO) and CdTe nanoparticles (NPs) through a simple one-step electrodeposition process. RGO film was formed on the top surface of TiO2 NT and CdTe NPs homogeneously dispersed within the RGO sheets and on the inner/outer walls of TiO2 NT. Resulting from the synergetic effect of RGO and CdTe, the photocatalytic activity of the ternary RGO/CdTe-TiO2 NT photocatalyst far exceeded those of bare TiO2 NT, RGO-TiO2 NT, and CdTe-TiO2 NT photocatalysts in the degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light or visible light irradiation. After 180-min UV-Vis (or visible light) irradiation, almost 100 % (or 96 %) 2,4-D removal efficiency was achieved on RGO/CdTe-TiO2 NT, much higher than 42 % (or 2 %) on bare TiO2 NT, 58 % (or 10 %) on RGO-TiO2 NT, and 52 % (or 41 %) on CdTe-TiO2 NT. This study will inspire better design of advanced photocatalysts with high visible-light photocatalytic activity.