In order to investigate the role of metal ions on a tartaric acid modified nickel catalyst, the enantio-differentiating hydrogenations of methyl acetoacetate and methyl levulinate were carried out. The effects of the addition of 17 metal salts of acetic acid on the enantio-selectivity and the hydrogenation rate were investigated during the hydrogenation of methyl acetoacetate. Among the examined metal salts, the addition of NaBr caused the great increase in the enantio-selectivity and the hydrogenation rate during the hydrogenations of both methyl acetoacetate and methyl levulinate. Based on the strength of the interaction between the metal salts of tartaric acid and the substrate, the sodium salts would have the strongest interaction with the substrate, hence, this would be attributed to the highest enantio-selectivity and hydrogenation rate for the sodium salts of tartaric acid.