It has been recently observed that infusion of spherical nanoparticles like TiO 2 has a positive effect in enhancing the mechanical and thermal properties of polyurethane foam. Since the particles were spherical in shape, the improvement in properties was global and almost isotropic in nature. In the present case, an attempt has made to investigate the effect of acicular nanoparticle like CNF on the properties of rigid polyurethane foam. Two different shapes of nanoparticles, namely, spherical TiO 2 and acicular Carbon Nanofiber (CNF), were infused to modify rigid polyurethane foam. TiO 2 nanoparticles are 29 nm diameter whereas CNF nanoparticles are 200 nm diameter with an aspect ratio of 500. The foam material has been manufactured from liquid polymer precursors of polyurethane which has two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). Nanoparticles were dispersed in part-A of liquid polyurethane in the amount of 1-wt% through an ultrasonic cavitation process. Once part-A was infused with nanoparticles, it was mixed with part-B with a mechanical stirrer, and was cast in a preheated rectangular mold to produce nanophased foam panels. A parallel set of control panels was also made with neat polyurethane foam. TGA and SEM studies were carried out to investigate the effect of spherical and acicular nanoparticles on thermal and microstructural properties of the foams. Finally, test coupons extracted from the panels were subjected to quasi-static and high strain rate compression (in the rise direction) over a wide range of strain rates varying from 10 -3 -1500 s -1 . There was a significant improvement in failure strength and energy absorption with both TiO 2 and CNF infusion. However, the enhancement in properties was noticeably higher with CNF infusion. Details of manufacturing and analyses of thermal and mechanical tests are described in the paper.