delta-Ni2Si nanowires have been synthesized via a co-reduction-silicification route, using anhydrous NiCl2 and SiCl4 as nickel source and silicon source, respectively, and metallic Na as reductant in an autoclave at 600 degrees C for 16 h. Transmission electron microscopy (TEM) observations show that the diameters of nanowires ranged in 10-100 nm and lengths up to several tens micrometers. The possible formation mechanism is discussed.