A new cadmium(II) coordination polymer, {[Cd(C(8)H(4)O(4))(C(12)H(8)N(2))(H(2)O)]·0.5C(8)H(6)O(4)}(n), has been synthesized under hydro-thermal conditions. The asymmetric unit contains one Cd(II) atom, one benzene-1,4-dicarboxyl-ate anion, one 1,10-phenanthroline ligand, one coordinated water mol-ecule and half of an uncoordinated benzene-1,4-dicaboxylic acid solvent mol-ecule. The Cd(II) atom is in the centre of a monocapped distorted octa-hedron made up of four O atoms of two chelating benzene-1,4-dicarboxyl-ate anions, one water O atom and two 1,10-phenanthroline N atoms. The metal centres are connected via bis-chelating benzene-1,4-dicarboxyl-ate anions into a zigzag chain structure along [001]. These chains are further connected by O-H⋯O hydrogen bonds between the water mol-ecules and adjacent carboxyl-ate O atoms. Additional O-H⋯O hydrogen bonding between the uncoordinated benzene-1,4-dicaboxylic acid mol-ecules along [010] consolidates the structure.