Design and preparation of highly active catalysts for hydrogen evolution reaction (HER) is very important for water splitting. Herein, we report a highly active HER catalyst, which is synthesized by loading nanostructured nickel phosphide (Ni2P) on three-dimensional few-layer graphene/nickel foam (G@NF). G@NF was successfully prepared by a chemical vapor deposition process in the presence of methane at high temperature. Compared with nickel phosphide, G@NF, as well as commercial platinum, the Ni2P-G@NF catalyst exhibited very high activity in electrocatalytic H2 production from water (~7 mV overpotential in alkaline solutions, pH ~14; and ~30 mV overpotential in acidic solution, pH ~0). The high catalytic activity of Ni2P-G@NF is attributed to the excellent performance of Ni2P, the large 3D framework which facilitates proton accessibility and electron transfer, and the high surface area.