Rational design of high-performance electrocatalysts with low cost and large abundance is highly desirable for water splitting technology. Here we report the synthesis of Ni3S2 pyramids coated with crimped graphene (Ni3S2@G), the unique configuration of which endows Ni3S2@G with large roughness, creating much more active sites along the edges. Moreover, the coupling of graphene enhances the electrical conductivity of the nanocomposite, and thus improves the electrocatalytic activity due to synergistic effect between graphene and Ni3S2. Ni3S2@G hybrid shows outstanding performance toward both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) with low overpotentials (eta(10) = 103 mV for HER and eta(20) = 294 mV for OER) and small Tafel slope. Ni3S2@G electrode also exhibits superior full water splitting ability with a low cell voltage of 1.66 V.