This work involves the study of mechanical and antibacterial properties of auxetic polyurethane (APU) foams synthesized using castor oil (CO) to ascertain their suitability as seat cushions in wheelchairs. Firstly, CO-based PU foams (PU-CO) were synthesized by substituting 25% synthetic polyol with CO in a polyol blend. Conventional PU foams and PU-CO foams were then converted to auxetic foams using triaxial compression and heating. The chemical composition, microstructure and thermal, mechanical and antibacterial properties of the foams were analyzed. It was found that addition of CO improved the antibacterial and mechanical properties of the foams. CO-based APU (CO-APU) foams showed highest compression strength and storage modulus. An increase in thermal stability of PU-CO was also observed as compared to PU foams. These CO-APU foams could be a better alternative to conventional PU foams for wheelchair seat cushions and in hospital bed applications. © 2021 Society of Industrial Chemistry. © 2021 Society of Industrial Chemistry.