Three Pt catalysts exhibiting similar metal particles size (<2 nm) were prepared on mesoporous supports differing by their chemical composition and tested in the liquid phase hydrogenation of cinnamaldehyde. The hydrogenation of the CC bond was favored with Pt/SBA-15 and Pt/Al-SBA-15, with significantly higher reaction rates on the latter catalyst. The acidic support changes the adsorptive properties of the platinum nanoparticles, modifying their surface electron density and possibly their morphology. In contrast, Pt/Al 2O3 was the most selective catalyst of the series toward cinnamyl alcohol, with CC and CO hydrogenations taking place at the same rate. The presence of Lewis acidic sites close to the particles is assumed to favor the adsorption of molecules via their polar CO bond. Even if cinnamaldehyde hydrogenation does not require acidic sites to be performed, the composition and acidity of the support significantly influence the reaction rate and selectivity.