A new two-dimensional manganese(II) coordination polymer, [Mn(μ-DEP)(μ-Cl)(H2O)2]n (1) (DEP is diethyl phosphate), was prepared from the reaction of MnCl2.4H2O and TEP (TEP is triethyl phosphate) ligand in mixture of H2O/CH3OH (1:10) at 40 °C. Suitable crystals of this complex for crystal structure determination were obtained by slow evaporation of the produced colorless solution at room temperature. Complex 1 was characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The X-ray structural analysis indicated that the manganese(II) is six-coordinated in a distorted octahedral configuration by four oxygen atoms from two water and two bridged diethyl phosphate ligands and two bridged chloride anions. Also, the thermal stability of 1 was studied by thermogravimetric and differential thermal analyses.