A high-performance bimetallic catalyst with mesoporous silica nanoparticles as support, PdAu/MSN, was prepared by an organic impregnation-hydrogen reduction approach. A series of investigations were conducted to assess the effects of (i) the porous nanoparticle support on the dispersion of active components and on the catalyst's performance, (ii) the addition of gold on the dispersion of active components and the catalyst's activity, and (iii) the preparation parameters, such as solvent, pressure, and temperature, on the catalyst's activity. The active metallic components were highly dispersed, with particle size 2.5 nm. The addition of gold to the catalyst favorably promoted the hydrogenation of cinnamaldehyde. The activity of PdAu0.2/MSN (with Au/Pd molar ratio 0.2:1) was up to four times higher than that of Pd/MSN (without Au as a promoter) and eight times higher than that of commercial Pd/C catalyst. The enhanced activity of PdAu0.2/MSN can be attributed to the synergistic effect of Pd with the added Au and the highly dispersed active components. The ultrahigh activity, as well as its novel structure with controllable compositions, makes this catalyst very attractive for both fundamental research and practical applications. (C) 2012 Elsevier Inc. All rights reserved.