A hydrothermal method was used to graft Ni nanoparticles onto the surfaces of carbon nanofibers (CNFs). The Ni nanoparticles have a narrow size distribution and are well dispersed over the CNF surfaces. Electrochemical capacitors were fabricated using CNFs and Ni-grafted CNFs as the electrodes. The electrochemical capacitance was enhanced due to the presence of the Ni nanoparticles. This is attributed to the occurrence of the pseudocapacitance effect, enhanced electric double layer capacitance, and increased electrical conductivity. The enhancement was proportional to the Ni content and can be as high as 214%. The stability of the Ni-grafted CNF capacitor was demonstrated by subjecting the capacitor to a potential sweep at 500 mV s(-1) for 500 cycles.