In the current study, flexible polyurethane foam was reinforced with different contents of SiO2 nanoparticles (0.5-2wt%). Compression test was performed in a range of strain rates (1-20min(-1)), and compression set test was also done at different temperatures. Results showed that addition of SiO2 nanoparticles improved compression properties of PU foam and the sample with 0.5wt% SiO2 nanoparticles exhibited the highest mechanical performance with about 180 and 40% improvements in the compressive plateau and densification stress. Strain rate was showing a positive effect on these parameters with the enhancements of 360 and 90%. It was also shown that the temperature had a remarkable effect on compression set behavior of nanocomposite as the values change from 0.5% at -20 degrees C to near 79% at 100 degrees C. Finally, microscopy micrographs confirmed the appearance of larger cell pores and a greater tendency for incomplete cell opening with increasing SiO2 content.