A series of new mixed ligand complexes of the ype [M(terpyridine H+) (amino acid)X2]-H20, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), X = Cl or NO3, have been synthesized and characterised by elemental analysis and infrared spectra. It is deduced that the coordination mode of the terpyridine is changed from terdentate in the binary complex to bidentate in the ternary one where the uncoordinated pyridine exists in the protonated form.