In this paper, ZnSe nanorods grown on in-situ synthesized ZnSe grains are reported. The ZnSe products are synthesized through thermal evaporation of elementary materials of Zn and Se powders in a horizontal resistance furnace. It is interesting to note that the ZnSe nanorods of nearly the same diameter and length are obtained, and they grow in the same direction on a facet of the ZnSe grain. The ZnSe grains are random in shape, with well-defined bounded facets. The ZnSe grains can be synthesized in various growth conditions while the ZnSe nanorods can be synthesized on the ZnSe grains with the fulfillment of the Zn enriched condition. The growth of ZnSe nanorods can be described by the self-catalytic vapor-liquid-solid (VLS) mechanism.