The reaction mechanisms occurring during the electrocatalytic oxidation of cellulose dissolved in a highly alkaline aqueous electrolyte were elucidated by hydrodynamic voltammetry using a Pt rotating disk electrode as well as product analyses. The charge-transfer limited current associated with the multielectron process in which macromolecules are cleaved into relatively short hydrocarbons was found to be dominant at relatively negative potentials, whereas further decomposition of the hydrocarbons proceeded at more positive potentials. Au was shown to facilitate the cleavage of cellulose macromolecules, while Pd and Ni promoted additional oxidative decomposition of the short-chain hydrocarbons. A fuel cell composed of Pt-deposited Ni foam electrodes as both the anode and cathode was capable of generating electricity in an external circuit while directly utilizing cellulose as a fuel, even at ambient temperature and pressure. The present study provides new insights into these reaction mechanisms and will assist in the design of catalytic materials intended for the effective utilization of biomass energy sources.