In the title complex, [Cu(C12H13NO5)(C12H8N2)]·0.5H2O, the CuII ion is five-coordinated by one N atom and two O atoms from a tridentate Schiff base ligand, derived from the condensation of l-threonine and o-vanillin, and two N atoms from a 1,10-phenanthroline ligand in a distorted square-pyramidal geometry. In the crystal, intermolecular O—H⋯O hydrogen bonds form a one-dimensional left-handed helical structureextending parallel to [001]. The water molecule of crystallization shows half-occupancy