A series of catalysts containing Au supported on Ni-based hydrotalcites (HT) Ni-Mg-Al varying in Ni content, but with a constant Mg2+/Al3+ ratio of 2, was prepared. Au nanoparticles were successfully formed and tested in the CO oxidation reaction. The effects of nickel content, HAuCI4 concentration, reduction pre-treatment and Au loadings were studied. The catalysts were characterized by XRD, BET, TPR, XPS and TEM. Au/Ni-Mg-Al hydrotalcites led to strongly enhanced activities for the CO reaction when compared with the bare support. Reduction of the catalyst increased the catalytic performance, contributing to an improved dispersion of gold as revealed by TEM. A significant difference in CO oxidation activity was observed which proved dependent on the HT precursor composition; the highest activity was found for the catalysts containing the lowest nickel content which correlated with the formation of Au particles of smaller size. The optimization of the preparation parameters (initial concentration of gold, gold loading, pre-treatment) allowed the successful deposition of 4 nm Au particles (Au/Ni0.06Mg0.94),very active for CO oxidation. (C) 2014 Elsevier B.V. All rights reserved.