A visible light-active photoelectrocatalyst, ZnFe-layered double oxide (LDO)/cobalt(II,III) oxide (Co3O4) composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide (LDH) prepared by a hydrothermal and microwave hydrothermal method. The morphological studies revealed that the ZnFe-LDO/Co3O4 composites exhibited a flower-like structure comprising Co3O4 nanowires and ZnFe-LDO nanosheets. Further, when the mass ratio of Co(NO3)2·6H2O/LDH was 1:1.8 and the calcination temperature was 550 °C, the ZnFe-LDO/Co3O4 composite exhibited 93.3% degradation efficiency for methylene blue (MB) at the applied voltage of 1.0 V under visible light after 3 h. Furthermore, the Mott-Schottky model experiments showed that the formation of a p-n heterojunction between ZnFe-LDO and Co3O4 could effectively inhibit the recombination of electrons and holes in the photoelectrocatalytic process. Meanwhile, free radical scavenging experiments showed that the active radicals of ⋅OH played an important role in the degradation of MB. Therefore, the photoelectrocatalytic effect of ZnFe-LDO/Co3O4 provides a simple and effective strategy for the removal of organic pollutants.