Herein we first report the synthesis of self-doped NaTaO3 nanoclusters using a facile and one-pot low-temperature solvothermal method. Ta(4+) in bulk NaTaO3 greatly narrows its band gap from 3.94 to 1.70 eV and thus extends its photoresponse from the UV to the visible light region, which leads to enhanced visible-light photocatalytic activity for water splitting and dye degradation without loading any co-catalysts such as Pt or NiO commonly used in the method described in the literature.