Eco-friendly synthesis in "one-pot" of 2-methyl-3-phenyl-propanal from benzaldehyde and propanal was studied using a multifunctional catalyst as an alternative to the three-step conventional process involving basic, acidic and hydrogenating catalysts. Mg(Al)O mixed oxides obtained from hydrotalcite precursor achieved the two first steps of condensation and dehydration. Addition of water to the solvent improves the activities and selectivities of Mg(Al)O, thanks to the reconstruction of the lamellar structure with OH- as compensating anions, acting as Bronsted basic sites. Mg(Al)O was then used as support for a multifunctional catalyst impregnated with Pd. Pd/Mg(Al)O led to 45% dihydrocinnamaldehyde selectivity at 43% conversion in benzaldehyde in the "one-pot" process.