The asymmetric unit of the title compound, C(12)H(8)N(2)·0.5C(2)H(4)N(2)S(2), contains one 1,10-phenanthroline mol-ecule and a half-mol-ecule of dithio-oxamide, which lies across a crystallographic inversion center. The 1,10-phenanthroline unit is not strictly planar, with dihedral angles between the central benzene ring and the pyridine rings of 1.42 (10) and 1.40 (10)°. In the crystal structure, two 1,10-phenanthroline mol-ecules are linked together by one dithio-oxamide via inter-molecular N-H⋯N hydrogen bonds.