The following results were obtained: (1) A commercial protease preparation gave the best enantioselective hydrolysis of N-acetyl-DL-methionine methyl ester (N-Ac-DL-MetOMe) to produce N-Ac-L-Met with > 99% e.e. (2) Solid NaHCO3 prevented chemical hydrolysis of N-Ac-DL-MetOMe. (3) N-Ac-L-Met was produced more efficiently when the pH was maintained at 7 with a mild base. (4) Crystalline N-Ac-L-Met and D-Met were simultaneously obtained with > 99% e.e. in 45 and 36% yield, respectively, from the reaction mixture.