In the title compound, [Cd(C16H16O3)(2)(C12H8N2)]center dot 4H(2)O, the Cd ion lies on a twofold rotation axis and is chelated by two monodeprotonated residues of the l-tyrosine-derived ligand (S)-2-[(2-hydroxybenzyl) amino]-3-(4-hydroxyphenyl) propanoic acid (L) in a kappa N-2,O amino acid chelating mode, exhibiting an (N,N')-trans disposition, and by 1,10-phenanthroline in a kappa N-2,N' mode. The latter ligand is also located about the twofold rotation axis that bisects the central six-members ring. The phenolic groups remain protonated and noncoordinating and take part as acceptors in the intramolecular hydrogen bonds with the amino groups of the acido ligands. The Cd ion is six-coordinated in a distorted octahedral environment. In the crystal, O-H center dot center dot center dot O hydrogen bonds result in the formation of three-dimensional network structures. The title complex has also been characterized by IR and H-1 NMR spectroscopy and DFT studies. The crystal studied was refined as an inversion twin.