Silicon nanowire arrays (SiNWAs) are under extensive investigation for solar cells and biomedical applications. This study reports for the first time that hydrogen fluoride-treated (H)-SiNWAs are an efficient catalyst for the reduction of nitrobenzene derivatives. We show that SiNWAs, after hydrogen fluoride treatment, have a high catalytic activity in p-nitrophenol (PNP) reduction. The conversion rate of PNP by H-SiNWAs increases with time and is almost complete within 30 min, which thus indicates catalytic activity comparable to that of platinum nanoparticles. The catalytic activity of SiNWAs is closely related to the chemical composition and specific morphology of the surface. SiH bonds on the surface are essential for activity, and arrays with longer nanowires showed a higher catalytic activity. Moreover, the activity can be easily regenerated by hydrogen fluoride treatment. It was also found that H-SiNWAs exhibit a similar catalytic activity for the reduction of other nitrobenzene derivatives such as p-nitroaniline and sodium m-nitrobenzenesulfonate. It is concluded that H-SiNWAs may be considered as an environmentally friendly alternative to noble-metal-based catalysts for the reduction of nitrobenzene derivatives.