Carbon-incorporated Co3O4 nanoparticles with an average diameter of 50 nm were prepared via a facile and environmentally friendly one-pot carbon-assisted method using degreasing cotton as a template as well as a reactant. The elemental analysis indicates the incorporation of carbon species into the Co3O4 nanoparticles and the XPS measurements demonstrate the presence of carbon species which comes from the incomplete combustion of the degreasing cotton. Interestingly, the resultant sample was able to split pure water into hydrogen under visible light irradiation without any cocatalyst, which is mainly due to the enhanced light absorption behavior confirmed by the UV-Vis absorption spectra. This facile method provided a potential strategy for applying narrow bandgap semiconductors in pure water splitting.