Due to various compositions and morphologies, exquisite intrinsic architectures, and renewability, biomass has been used to generate carbon electrodes for supercapacitors. This review focuses on the latest achievements in the synthesis and application of biomass-derived carbons and composites as supercapacitor electrodes. Particularly, the impact of merits of biomass-derived carbon (high specific surface areas and porosity, doping with different heteroatoms, conductivity, and different nanostructures) on the electrochemical properties of composites is systematically introduced. Thereafter, advances in composites of biomass-derived carbons with graphene, carbon nanotubes, transition metal oxides, and conducting polymers are thoroughly surveyed. Finally, challenges and outlooks towards the future development of biomass-derived carbon materials are discussed.