Manganese dioxide nanofibers with length ranged from 0.1 to 1μm and a diameter of about 2–4nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of slurries of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNTs) into porous nickel foam current collectors. In the composite electrodes, MWCNT formed a secondary conductivity network within the nickel foam cells. Obtained composite electrodes, containing 0–20wt.% MWCNT with total mass loading of 40mgcm−2, showed a capacitive behavior in the 0.1–0.5M Na2SO4 solutions. The highest specific capacitance (SC) of 155Fg−1 was obtained at a scan rate of 2mVs−1 in the 0.5M Na2SO4 solutions. The SC increased with increasing MWCNT content in the composite materials and increasing Na2SO4 concentration in the solutions and decreased with increasing scan rate.