A phosphorus-containing flame retardant 2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dimethanol, alpha,alpha,alpha',alpha'-tetramethyl-3,9-dioxide (DPDM) was synthesized. The structure and the thermal stability of the compound were characterized by infrared spectroscopy (IR), nuclear magnetic resonance (H-1 NMR), mass spectroscopy (MS), elemental analysis, and thermogravimetric analysis. Using a static analytical method, the solubilities of DPDM in acetic acid + acetone binary mixtures, water, methanol, and ethanol were determined in the temperature range from (293.14 to 338.14) K. The solubility data were correlated with an empirical equation.