The rational modulation of composition and structure is critical for the development of robust and efficient oxygen evolution reaction (OER) catalysts for water splitting. In this study, an onion-like N-doped carbon nanorods hybrid (denoted as ONC) with encapsulated Ni/Fe3O4 heterostructures has been fabricated by the pyrolysis of an NiFe-based coordination polymer under a N2 atmosphere. The nanorod-like morphology is transferred from the polymer to the hybrids and generates ONC nanolayers encapsulated with core-shell Ni/Fe3O4 nanostructures. The synergistic effects between the ONC layers and the encapsulated Ni/Fe3O4 heterostructures result in high electronic conductivity due to the nitrogen-doped carbon with an appropriate level of defects and enlarged electrochemical surface area due to the well-defined mesoporous morphology. Compared with Ni@ONC, Fe3O4@ONC, NiFe2O4 and commercial RuO2 electrocatalysts, the as-prepared Ni/Fe3O4@ONC exhibits extraordinary electrocatalytic activity for water oxidation with an overpotential of merely 296 mV at 10 mA cm-2 and a small Tafel slope of 61 mV dec-1. This Ni/Fe3O4@ONC OER catalyst highlights the great potential of integrating hetero-composite nanocatalysts with hetero-atom doped nanocarbon supports for the development of high-performance electrocatalysts for renewable energy applications.