Five-coordinate trigonal-bipyramidal palladium(II) L-cysteinato and glutathionato complexes with tris(2-(diphenylphosphino)ethyl)phosphine have been prepared. The high selectivity for the thiolato sulfur atom in the axial position has been confirmed and was applied to separation of L-cysteine from the other amino acids and selective determination of the reduced form of glutathione.