The present disclosure relates to a polypeptide having an acyltransferase activity or a microorganism including the same; a composition for preparing N-acetyl-L-methionine, the composition including the polypeptide or microorganism; and a method of preparing N-acetyl-L-methionine using the polypeptide or microorganism. Further, the present disclosure relates to a polynucleotide encoding the polypeptide and an expression vector including the polynucleotide. Since the microorganism including a novel acyltransferase according to the present disclosure has enhanced acyltransferase activity, this microorganism can be efficiently used for producing N-acetyl-L-methionine by acetylating L-methionine.