A novel 3D supramolecular complex di(thiocyanato-kappa N)bis(1,10-phenanthroline-5,6-dione-kappa N-2,N')manganese(II) with molecular formula [(C12H6N2O2)(2)Mn(NCS)(2)](2), was formed by the reaction of 1,10-phenanthroline-5,6-dione with Mn(NCS)(2), in which metal ion was in a sixcoordinated environments with a distorted octahedral geometry. Then independent mononuclear units are linked each other and pack in 3D-superamolecular network via hydrogen bonds interactions. The crystal is monoclinic. space group C2/c with unit cell parameters: a = 33.371 (3) angstrom, b = 8.8648 (8) angstrom, c = 18.7352 (18) angstrom, alpha = 90 degrees, beta = 116.137 (1)degrees gamma = 90 degrees, V = 4975.6 (8) angstrom(3), Z =4, Mr = 1182.95, Dc = 1.579 g/cm(3), mu = 0.746 mm(-1), F(000) = 2392, R = 0.0431, wR = 0.1085 for 4363 reflections with I > 2 sigma(1).