The effect of surface modifications of carbon black (CB) on its dispersion in polyether polyol and CB/polyurethane (PU) foams and the properties of the CB/PU composite foams was investigated. Pristine CB (p-CB) was oxidized in nitric acid to obtain oxidized CB (o-CB), and then by the esterification reaction between the carboxyl groups of o-CB and the hydroxyl groups of polyether polyol, polyol grafted CB (g-CB) was obtained. Optical microscopy, scanning and transmission electron microscopy observations showed that surface modifications effectively improved the dispersion of CB in polyether polyol and in the final composite foams. Compared with the p-CB/PU foams, the o-CB/PU and g-CB/PU composite foams exhibited improved conductivities, storage moduli, and increased glass transition temperatures. The compressive strengths of the p-CB/PU and o-CB/PU composite foams decreased with the increase of filler contents, but g-CB has no negative effect on the compressive strength even at a filler content as high as 8 phr. Furthermore, the cell sizes for the o-CB/PU and g-CB/PU composite foams were more uniform than those of p-CB/PU foams.