Unsymmetrical indamine dyes have been synthesized by the reaction of (diethylamino)thiazole dimer with 4-nitrosoanilines followed by heating with metal salts. The chromophoric system for these indamine dyes was described as the mixture of the pi-pi* transition coming from the alternant chromophore inside the bithiazolyl moiety and the charge-transfer from anilino to bithiazolyl moieties.