External additives (i.e., ionic electride donors) are usually necessary to obtain a high catalytic performance in an electron-density-dependent chemoselective hydrogenation reaction. Here, a sphere-shaped Pt/Fe3O4 catalyst is prepared through a one-pot redox reaction using Pt(IV) and Fe(II) precursors. The experimental results show that the prepared Pt/Fe3O4 catalyst with an Fe to Pt mole ratio of 100 : 1 can afford a high conversion of 94.2% towards cinnamaldehyde (CAL) and good selectivity of 92.2% towards cinnamyl alcohol (COL) under the mild conditions of 303 K, 5 bar H2 for 150 min in the chemoselective reduction of CAL. The excellent catalytic performance could be attributed to the dissociation of H2 and adsorption of CAL via a vertical configuration modulated by the electronic effect between Pt and Fe3O4, and the abundant available active sites induced by uniformly dispersed Pt nanoparticles. Additionally, the intrinsic magnetism of Fe3O4 nanospheres endows the catalyst with a rapid separation property, favourable for repeated use of a catalyst.