Dimer fatty acid (DA)-based polyester polyols (DAP and DAP-Gs) were prepared successfully by DA and 1,6-hexanediol-glycerol through an esterification reaction. The structure elucidation of DAP and DAPGs was analyzed by Fourier transform infrared (FTIR), Nuclear magnetic resonance (NMR) and acid and hydroxyl values. To study the effect of chain extender on the final coating properties, a series of dimer acid-based PU (DAPU-G) coatings was prepared by incorporating glycerol in varying percentages (10 − 30 wt%) to DAP and crosslinked with hexamethylene diisocyanate-biuret (HDI-B). The motive of this finding was to study the effect of chain extender with DAP polyol on physico-mechanical, chemical resistance, crystallinity, and thermal performance of PU coatings. The results show that the incorporation of chain extender improved the final properties of PU coatings. Upon evaluating chemical resistance and coating properties, it was established that DAPU-G (10 − 30 wt%) coatings showed excellent performance compared to DAPU due to its higher crosslink density network. The thermal analysis outcomes exhibit that the glass transition temperature (T g ) and thermal stability of PU coatings increased by adding a chain extender. Furthermore, the addition of a chain extender increased the chemical and water resistance property of PU coatings. Tensile properties of PU coatings increased from 14.7 − 30.68 MPa; meanwhile, elongation at break decreased from 8.3 to 4.8% with increment in glycerol content. This study exhibited that glycerol can substitute a partial petrochemical chain extender as a bio-based chain extender to prepare PU with an excellent coating performance.