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Abstract The present study investigates the properties and structure of condensation non-isocyanate polyurethanes (NIPURs) prepared by reacting 2-hydroxy-6-naphthalenesulfonic acid (HNSA) with phenolsulfonic acid, urea and formaldehyde. Instrumental analyses confirmed a linear and segmented structure of the obtained condensation NIPURs. It was found that NIPUR films containing 20% HNSA and an equimolar ratio of rigid to flexible segments exhibited maximum values of tensile strength and tensile strain at break. All prepared samples showed a very high water resistance. The operating temperature of NIPUR samples based on HNSA was set between -33°C and +145°C. The first temperature was attributed to the glass transition of flexible segments, while the second one was associated with rigid segments melting. The higher the transition temperature, the higher the rigid segment content and the higher the HNSA content in the NIPUR sample.