The change in structural and surface properties of Pd/Al2O3 catalysts as the effect of reduction in liquid phase during preparation is investigated by a multi-technical approach. It has been found that, although the treatment leaves an external shell of oxidized Pd because of the exposure to air of final wet catalyst, it affects both the catalyst reducibility and the properties of the supported Pd nanoparticles, in terms of dispersion, particle size, morphology, interaction with the support, structural order, and surface properties. Consequently, unreduced and pre-reduced catalysts show different performances in the debenzylation of 4-benzyloxyphenol reaction.