Diethylchlorotin dimethylphosphinate has been synthesized by treating (Et2ClSn)2O with HO2PMe2 in toluene. Single crystal X-ray analysis shows that O2PMe2 groups behave as bidentate bridge ligands between Et2ClSn units leading to a polymeric chain structure in which the tin atoms exhibit a distorted trigonal bipyramidal geometry with the oxygen atoms in the axial positions. The Sn-Cl bond lies on a C2 axis of symmetry in the (C2v) OCClSnCO unit. Et2ClSnO2PMe2 crystallizes in the monoclinic space group C2/c (a = 877.9 (2), b = 1907.8 (4), c = 695.5 (1) pm, β= 106.72 (2)°, Z = 4 and R = 0.043). The characteristic IR bands of Et2ClSnO2PMe2 are assigned and the mass spectrum is reported and discussed.