Using microwave irradiation, PtCo alloy nanoparticles were deposited within a few minutes on COOH-functionalized MWCNT supports. The obtained catalysts were used for selective hydrogenation of cinnamaldehyde, a reaction whose products are widely used in various fields. In the selective cinnamaldehyde hydrogenation to cinnamyl alcohol, microwave-prepared catalysts (generically, PtxCoy-MW) outperformed a catalyst prepared by the conventional method (Pt1Co2-con). The highest selective hydrogenation to cinnamyl alcohol, 89%, was obtained using Pt1Co2-MW, while Pt1Co2-con showed a selectivity of 76%. Characterization results confirmed that the microwave prepared samples had a stronger interaction between Pt and Co than that in the Pt1Co2-con sample. The alloyed Co altered the electronic structure of Pt, leading to favorable adsorption of the C=O bond by the lone-pair electrons of its oxygen atom. Moreover, the Pt1Co2-MW sample showed neglectable change in catalytic performance (e. g., cinnamaldehyde conversion and selective hydrogenation to cinnamyl alcohol) during recycling experiments.