To enhance the intrinsic activity and the density of active sites of catalysts for the hydrogen evolution reaction (HER), a facile strategy of using an organic–inorganic precursor followed by carbonization is adopted to prepare ternary core–shell nanostructures composed of ultrafine hybrids of MoNi alloys and MoC_x nanoparticles encapsulated in N-doped carbon nanospheres (MoNi_x–MoC_x@NC). The well-defined pitaya-like nanostructures of MoNi_x–MoC_x nanoparticles encapsulated by N-doped carbon nanospheres can be obtained with MoNi_x–MoC_x hybrids as the core and ultrathin N-doped C layers as the shell. A triple synergistic effect has been achieved for the HER. The first synergistic effect from homogeneously dispersed MoNi_x alloys and MoC_x nanoparticles can improve the intrinsic activity and conductivity of MoC_x. The second synergistic effect from the MoNi_x–MoC_x and NC shell can enhance the density of active sites and conductivity of MoNi_x–MoC_x. The third synergistic effect from N-doped C can accelerate the charge transfer rate and improve close interaction between NC and MoNi_x–MoC_x. The MoNi_x–MoC_x@NC sample at an optimized low temperature of 700 °C exhibits excellent performance and long-term stability in both acidic and alkaline solution. It requires a lower overpotential of only 172 mV and 168 mV at 10 mA cm⁻² in acidic and alkaline solution, respectively. This work provides a new approach to design multiple synergistic effects from excellent catalytic interface through an organic–inorganic hybrid method for efficient electrocatalysis.