Based on the hydrogen spillover effect, versatile binary-site catalysts are promising for the alkaline hydrogen evolution reaction (HER). In which one site can adsorb and dissociate water, while the neighboring site is favorable for liberating hydrogen. Inspired by these possibilities, oxygen vacancy (Ov)-rich LaCeOx coupled N-doped graphene/Ru single-atoms (LaCeOx @NGr/Ru1) was synthesized as an efficient dual-site HER catalyst. It delivered an impressive low overpotential of 22 mV at a current density of 10 mA cm−2 and a slight Tafel slope of 40 mV dec−1 in an alkaline medium, outstanding the advanced Ru-based catalysts. Moreover, this promising binary-component catalyst exhibited higher mass activity and longer lasting durability than commercial Pt/C catalyst (20 wt%). Experimental and theoretical investigations provided insights into the HER mechanisms of LaCeOx @NGr/Ru1 based on three indispensable steps: water adsorption and dissociation on Ov-rich LaCeOx, diffusion of generated H* species towards Ce3+-N-Ru1 bridges, and hydrogen evolution on Ru1 sites.