The development of efficient and stable non-precious bifunctional electrocatalysts for overall water splitting is highly desirable but remains challenging. Herein, a ternary composite material comprising Co (VO3)2, CoO, and Co3O4 phases (denoted as CVO-CoOx) was in-situ constructed on nickel foam via a facile hydrothermal approach. The introduction of vanadium is crucial for directing the formation of a well-defined three-dimensional nanosheet architecture, in sharp contrast to the nanoparticle-aggregated morphology of the vanadium-free CoO/Co3O4 reference. Comprehensive characterization confirms the successful integration of multiple phases and reveals strong electronic interaction among them, characterized by electron transfer from Co to V and an increased concentration of defect-associated oxygen species. Benefiting from these synergistic effects and the optimized electronic structure, the CVO-CoOx/NF electrode delivers outstanding bifunctional electrocatalytic activity in 1.0 M KOH, requiring overpotentials of only 230 mV for the hydrogen evolution reaction (HER) and 310 mV for the oxygen evolution reaction (OER) to reach 100 cm−2. Furthermore, CVO–CoOx/NF exhibits excellent long-term stability over 32 h for HER and 24 h for OER. This work illustrates an effective strategy for designing high-performance non-precious-metal multiphase heterostructures for sustainable electrochemical hydrogen production.