Self-assembling phenylalanine-based peptides have garnered interest owing to their potential for creating new functional materials. Here, we designed four diastereomers, L-Phe-L-Phe-L-Phe (FFF), D-Phe-LPhe- L-Phe (fFF), L-Phe-D-Phe-L-Phe (FfF) and L-Phe-L-Phe-D-Phe (FFf), to analyze the effect of the D-isomer on the self-assembly. Using SEM, TG, VCD, and solid-state NMR measurements, we found that only FFf forms a c-turn conformation and self-assembles into a nanoplate with higher thermal stability. The supramolecular structure of FFf consists of intra-and intermolecular hydrogen bonds and p-p stackings. From our results, we have discovered that FFf forms a new type of self-assembling c-turn conformation, clarifying the structural role of a D-amino acid residue in supramolecular formation.