Indium oxide (In2O3) doped zinc oxide (ZnO) nanocomposites were successfully synthesized through a facile microwave hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N-2 adsorption-desorption isotherms (BET) and UV-Vis diffuse reflectance spectroscopy. The morphology of In2O3-ZnO composites was observed to be like flowers, and the diameter of particles constituting the porous petal was about 30 nm. The photoelectrocatalytic test results showed that the photoelectrocatalytic methylene blue (MB) degradation efficiency using In2O3-ZnO nanocomposites as photocatalysts under visible light irradiation and a certain voltage could reached above 95.3% after 60 min, much higher than that of In2O3 particles and ZnO particles. The enhanced photoelectrocatalytic activity was attributed to the doping of In2O3 and applied voltage, which beneficially reduced the recombination of electrons and holes in the photoelectrocatalytic process, therefore, it promoted the production of active species (center dot OH and center dot O-2(-)). (C) The Author(s) 2019. Published by ECS.