This work reports one-step synthesis process of LiOH-castor oil based polyurethane foam (PU) by completely replacing synthetic polyol. The reaction involved reacting varying weight percentage of lithium hydroxide with castor oil along with isocyanate. The successfully synthesized stable PU foams were characterized for density, sol fraction, cellular morphology, polymer phase morphologies and thermo-mechanical properties. The properties of the LiOH-castor oil based PU foams were compared with the conventional PU foam. Flexibility of the synthesized foams was observed to be lower than conventional PU foam for 0.05%, 0.1% and 0.5% LiOH due to the presence of closed cells with pin holes. Whereas, presence of open cellular structure in 0.3% LiOH-castor oil based PU foams showed flexible nature. Sol fraction of all the synthesized foams was found low (~ 5%) indicating improved reactivity. Thermal conductivity, glass transition temperature, thermal stability and mechanical properties of the synthesized PU foams suggest the possibility of replacing conventional PU foams for various applications. © 2021, The Polymer Society, Taipei.