The hydrogenation of methyl oleate into oleyl alcohol was studied in the presence of a CoSn catalyst at 270 degrees C and 8.0 MPa. The selectivity of the CoSn catalyst to oleyl alcohol is comparable to that of the RuSn catalyst but the CoSn catalyst is less active. The activity and the selectivity to unsaturated alcohol was maximum for an atomic Sn/Co ratio of 1. Nevertheless, the side reaction, the transesterification between methyl oleate and alcohol, still occurs in the presence of CoSn catalysts. The method of preparation influenced the activity, impregnation and reduction with sodium borohydride dry>impregnation>sol-gel technique, but the oleyl alcohol yields, obtained over the catalyst reduced with sodium borohydride or over the catalyst prepared by a sol-gel technique, are similar. From XPS analysis, Co-0 and two tin-oxide species were identified at the surface of the CoSnB/Al2O3 catalyst after reduction with sodium borohydride. The addition of tin species does not modify the surface cobalt content. The reduction with sodium borohydride increased the reducibility of the metal oxide species.