We reported the synthesis of organic–inorganic polyurethanes with polyhedral oligomeric silsesquioxane (POSS) in the main chains. Toward this end, 3,13-dihydroxypropyloctaphenyl double-decker silsesquioxane (DDSQ) was synthesized; this POSS diol was used as a chain extender to obtain hybrid polyurethanes with DDSQ in the main chains. By controlling the molar ratio of 3,13-dihydroxypropyloctaphenyl DDSQ to 1,4-butanediol (BDO), organic–inorganic polyurethanes were obtained with a content of DDSQ up to 48 wt%. The results of 1H nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) showed that 3,13-dihydroxypropyloctaphenyl, DDSQ, can be successfully used as a chain extender to afford linear organic–inorganic polyurethanes. Differential scanning calorimetry (DSC) showed that the organic–inorganic polyurethanes displayed enhanced glass transition temperatures (Tg's) compared to control polyurethane; the Tg's increased with increasing content of DDSQ in the main chains. Compared to control polyurethane, the organic–inorganic polyurethanes displayed improved thermal stability in terms of thermogravimetric analysis (TGA). With the inclusion of DDSQ in the main chains, the organic–inorganic polyurethanes displayed enhanced surface hydrophobicity.