A new manganese(II) complex [Mn(C₁₄H₉O₃)₂(C₁₂H₈N₂)₂]·4H₂O (1) was synthesized with o-ben- zoylbenzoic acid, manganese sulfate and 1,10-phenanthroline (phen) in the mixture of acetonitrile and water solvent. It crystallizes (C₅₂H₄₂MnN₄O₁₀, M_r = 937.83) in monoclinic, space group P2₁/n with a = 13.3528(5), b = 17.6963(6), c = 19.7889(7) Å, β = 109.647(4)º, V = 4403.8(3) ų, D_c = 1.415 g/cm³, Z = 4, F(000) = 1948, μ(MoKα) = 0.368 mm^-1, R = 0.0404 and wR = 0.0956. The crystal structure shows that the manganese ion is coordinated with two oxygen atoms from two o-benzoylbenzoic acid molecules and four nitrogen atoms from two phen molecules, forming a distorted octahedral coordination geometry. The TG, spectrum analysis and magnetic properties of 1 were studied.