Polyaniline coated mesoporous and microporous activated carbons were prepared by chemical oxidation polymerization of aniline adsorbed on activated carbons. BET and mesopore specific surface areas of the obtained activated carbons decreased by coating with polyaniline. The electrode performance of the polyaniline coated activated carbons for supercapacitor was investigated. The electrochemical pseudo-capacitances increased with increasing polyaniline content in activated carbons. The capacitances due to polyaniline in the mesoporous activated carbon are much higher than those in the microporous activated carbon. The uniform coating of polyaniline on mesopores of activated carbon plays an important role in pseudo-capacitance due to polyaniline.