Research interest in two-dimensional (2D) materials has grown exponentially across various fields over the past few years. In particular, 2D phosphorene, the single- or few-layered analogue of semiconducting black phosphorus (BP), holds specific promise for advanced catalysis reactions including electrocatalytic hydrogen (H2) production. However, bare phosphorene nanosheets suffer from poor electrical conductivity, limited catalytic sites and instability under ambient conditions. Herein, we integrate ultrathin few-layer BP (FL-BP) nanosheets with boron-doped graphene (BG) to form a novel metal-free 2D/2D heteroelectrocatalyst for the hydrogen evolution reaction (HER) in acidic media. Our newly designed electrocatalyst (FL-BP@BG) shows remarkably enhanced HER activity with a low overpotential of 385.9 mV at 10 mA cm−2, while exhibiting a low charge transfer resistance of only 5.5 Ω in H2SO4 electrolyte. In addition, the FL-BP@BG catalyst shows an outstanding stability over 500 continuous cycles, demonstrating that hybridizing FL-BP with BG is an efficient strategy to construct stable BP based electrocatalyst. This work paves the way for emerging 2D materials for advanced catalysis systems.