InAs nanofibers were prepared at 160 °C through a new route: 2InCl3 + 6KBH4 + 2As 2InAs + 6KCl + 6BH3 + 3H2. The products were characterized as zinc blende phase by X-ray powder diffraction (XRD). Transmission electron microscopy (TEM) images showed that the products were polycrystalline fibers or near-single-crystal whiskers with widths of 15−100 nm and lengths of 150−1000 nm. There is trace indium coexisting with the products, indicating that the reaction proceeds through a metallic indium intermediate. When the reaction temperature was lowered to 120 °C, which is below the melting point of indium, spherical InAs nanocrystals with diameters of 20−50 nm were prepared. A solution−liquid−solid (SLS) mechanism is proposed for the fiber growth. The composition of the products was analyzed by X-ray photoelectron spectroscopy (XPS).