An efficient Cu(I) complex-promoted intramolecular cyclization reaction of β-keto trifluoromethyl amines has been developed, providing access to a series of unprotected trifluoromethylated aziridines with good chemical yields and excellent stereoselectivity (trans : cis > 99 : 1). The reaction can be carried out under mild conditions and tolerates a wide range of substrates with diverse functional groups, representing a straightforward method for the preparation of trifluoromethylated aziridines from readily available starting materials.