The rational design of high-performance electrocatalysts based on nonprecious metals is a key for the development of water-splitting technology. In this work, porous nickel-cobalt nitride–oxide (NiCo–N–O) nanosheet hybrids in a networked configuration are synthesized on carbon cloth through in situ plasma treatment of nickel-cobalt layered double hydroxide (LDH) precursors. The self-supported NiCo–N–O electrodes exhibit the outstanding catalytic activity of hydrogen evolution reaction (HER) with a low overpotential of 50 mV at 10 mA cm−2 in alkaline conditions. The synergistic effects of the morphology, microstructure, and electron transfer between nickel-cobalt nitride and oxide and the favorable role of introducing bimetallic Ni and Co sites on the enhanced electrocatalytic activities are discussed. This work provides a simple and feasible pathway to prepare porous bimetal nitride–oxide hybrid HER electrocatalysts with high efficiency and stability. Display omitted •Porous nickel-cobalt nitride–oxide (NiCo–N–O) hybrids are synthesized through in situ plasma treatment of LDH precursors.•Self-supported NiCo-N-O electrode delivers superior performance and favorable stability of HER.•The synergistic effects of the morphology, microstructure, and electron transfer between nickel cobalt nitride and oxide are discussed.