Novel nanostructured material WS2 nanosheets (NSs) were prepared through a simple and highly reproducible approach, namely, a mechanical activation strategy by using WO3 and S as the starting materials, and were explored as electrocatalyst for hydrogen evolution reaction (HER). The as-prepared WS2 NSs reveal separate NSs nanostructure with a sheet thickness of less than 10 nm. On the basis of experimental results obtained under various synthesis conditions, a reasonable reaction process and formation mechanism is proposed, in which the pre-treatment of ball milling is assumed to play a key role for the formation of WS2 NSs. Due to its large active sites originating from its unique structural characteristics such as loosely stacked layers, providing highly exposed rims particularly edges, WS2 NSs catalyst has demonstrated high electrocatalytic activity toward HER, which considerably outperforms the commonly used MoS2 (JDC) catalyst. (C) 2012 Elsevier B.V. All rights reserved.