Spinel Co3O4 nanoparticles prepared by solution phase method having particle size in the range of 12-20 nm exhibited excellent activity for the liquid-phase aerobic oxidation of vanillyl alcohol with 80% conversion and 98% selectivity to vanillin. Our catalyst could be reused three times without appreciable loss in activity. The catalytic activity of the Co3O4 nanoparticles was found to be similar to its homogenous precursor (cobalt acetate) and greater than the commercial Co3O4 oxide. The detailed characterization results of morphology, size and structure of the prepared Co3O4 nanoparticles obtained by XRD, FT-IR, H-2-TPR, HR-TEM and cyclic voltammetry technique were used to understand the roles of various Co species in directing the selectivity towards vanillin.