New thermoplastic segmented poly(azo-urethane)s (PAUs) have been synthesized by one-step polycondensation from aromatic diazo-diol, ( E)-1-(4-(4-(3-hydroxypyridyl-azo)thiocarbamoylaminobenzyl)-phenyl)-3-(3-hydroxypyridylazo)thiourea, as chain extenders, phenylene diisocyanate and 20–60 mol % polyethylene glycol (PEG) with the molecular weight of 2000 g/mol. The effect of diazo-diol used in the structure and some physicochemical, thermal and mechanical properties of the segmented polyurethanes were studied. The structure was examined by proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR) analyses. Polyazos were the products with good processability and high molar mass in the range 120 × 103–135 × 103 g/mol. Thermal properties, investigated by thermogravimetric analysis and differential scanning calorimetry indicated that PAUs up to 40 mol % polyol were fairly stable above 530°C, having initial weight loss of around 528–539°C, 10% gravimetric loss in the range 553–567°C and own high glass transition temperature 259–264°C. The polymers also demonstrated higher tensile strength (56.53–63.83 MPa) and elongation at break (1.58–1.63). However, compared with typical polyurethanes, PAUs with lower polyol content displayed higher Tgs, heat and mechanical stability owing to warily designed rigid hard segment structure.