The effect of FeOx on the activity and selectivity in the cinnamaldehyde hydrogenation over Ir/SiO2 catalyst was studied. FeOx/SiO2, Ir/FeOx/SiO2 and Ir/SiO2 catalysts were prepared by impregnation. Fe and Ir content by weight% was 5%Fe and 1%Ir respectively. Samples were calcined at 673 K and reduced in H2 at 573 K. All catalysts were characterized by N2 adsorption, TEM, H2-TPR and DRIFTS of CO at room temperature. Cinnamaldehyde hydrogenation was carried out at 363 K in a batch reactor. The presence of FeOx has practically no effect in the conversion, but the selectivity to the desired unsaturated alcohol changes drastically when FeOx/SiO2 is the support. In addition, selectivity toward unsaturated alcohol increased with the conversion for Ir/SiO2 catalyst while for Ir/FeOx/SiO2 catalyst remained constant. A combination of particle size effect and the presence of Fen+ sites in proximity of iridium sites are responsible for the preferential hydrogenation of the CO bond over Ir/FeOx/SiO2 catalyst. Keywords: Cinnamaldehyde, Heterogeneous catalysis, Hydrogenation, Ir/FeOx/SiO2, Ir/SiO2.