A new complex [Ni(phen)3]2+·(ClO4 -)2 has been synthesized by the reaction of Ni(OAc)2·(H2O)4 with 1,10-phenanthroline in the CH3CH2OH/H2O (v:v = 5:1). It was characterized by elemental analysis, IR and X-ray single crystal diffraction analysis. The crystal of the title complex [Ni(phen)3]2+·(ClO4 -)2 belongs to monoclinic, space group C2/c with a = 3.6602(7) nm, b = 1.5762(3) nm, c = 1.2230(2) nm, β = 102.75(3) º, V = 6.882(2) nm3, Z = 8, Dc = 1.541 μg·m-3, μ = 0.783 mm-1, F(000) = 3263, and final R1 = 0.0985, ｗR2 = 0.2872. The complex comprises a six-coordinated Ni (II) center, with a N6 distorted octahedron coordination environment. The molecules are connected by π-π stacking to form one dimensional chain structure.