N‐terminal thiourea‐modified l‐Leu‐based peptide {(3,5‐diCF₃Ph)NHC(=S)‐(l‐Leu‐l‐Leu‐Ac₅c)₂‐OMe} with five‐membered ring α,α‐disubstituted α‐amino acids (Ac₅c) catalyzed a highly enantioselective 1,4‐addition reaction between β‐nitrostyrene and dimethyl malonate. The enantioselective reaction required only 0.5 mol % chiral peptide‐catalyst in the presence of ⁱPr₂EtN (2.5 equiv.), and gave a 1,4‐adduct with 93 % ee of an 85 % yield. As Michael acceptors, various β‐nitrostyrene derivatives such as methyl, p‐fluoro, p‐bromo, and p‐methoxy substituents on the phenyl group, 2‐furyl, 2‐thiophenyl, and naphthyl β‐nitroethylenes could be applied. Furthermore, various alkyl malonates and cyclic β‐keto‐esters could be used as Michael donors. It became clear that the length of the peptide chain, a right‐handed helical structure, amide N−Hs, and the N‐terminal thiourea moiety play crucial roles in asymmetric induction.