Fluorescence labeling of proteins is a useful tool for protein structural and functional analysis. We developed here a novel method to attach a fluorescence labeling at the N terminus of proteins through the incorporation of a fluorescent hydroxy acid and subsequent hydrolysis of the ester bond in a cell-free translation system. We found that N-terminal tagged proteins containing p-(BODIPYFL-amino)-L-phenyllactic acid at the downstream of the tag peptides were efficiently synthesized and the resulting ester bonds were hydrolyzed during the translation reaction. These results indicate that the present method will become a useful tool for the N-terminal specific labeling of proteins.