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The development of carbon-based catalysts with excellent activity for hydrogen evolution reaction (HER) is highly desirable but still remains a significant challenge. Chemical doping and morphology engineering are paramount to enhance their catalytic performance toward HER. Herein, we present a novel and effective strategy to synthesize heteroatoms-doped three-dimensional (3D) carbon nanotubes/graphene hierarchical architecture (N,S-CNTs/N,S-G) on layered double oxide substrates, in which the N,S-doped CNTs are in-situ grown on both sides of N,S-doped graphene, by two differentiated chemical vapor deposition (CVD) processes. The high concentrations of N and S dopants (up to 6.5 at.%) provide sufficient catalytic active sites for HER, while the CNTs seamlessly grafted on graphene ensure the excellent electric conductivity of N,S-CNTs/N,S-G hybrids. Consequently, the 3D N,S-CNTs/N,S-G composites display superior electrocatalytic activity for HER with an onset potential of 62 mV vs. RHE (achieve current density of 1 mA cm−2) and a small overpotential of 126 mV at 10 mA cm−2, which outperforms most of reported chemical doped carbon-based composites. The synthetic strategy facilitates the fabrication of other heteroatoms-doped 3D electrochemical catalysts. The hierarchical architecture formed by CNTs anchoring on graphene greatly impedes the aggregation of CNTs and stacking of graphene sheets, ensuring the exposure of catalytic active sites in both CNTs and graphene sheets. The synergistic N, S co-doping successfully increases the active sites and enhances the electron transfer, and thus significantly improving the HER catalytic activities of N,S-CNTs/N,S-G hybrids. Image 1 • The CNTs are in-situ welded on both sides of graphene by C–C covalent bonding. • There are high concentrations of N and S dopants in N,S-CNTs/N,S-G. • N,S-CNTs/N,S-G composites display superior electrocatalytic activity for HER. [ABSTRACT FROM AUTHOR]