We demonstrate that C,N-codoped InOOH microspheres could be prepared by using a facile citric acid assisted hydrothermal method at 220 °C. The citric acid could not only act as a complexing agent to control the morphology and the size, but also serve as a carbon source and a reducing agent for C and N codoping. The codoping could be successfully tuned by the amount of citric acid. Interstitial N and surface carbonaceous species were found in the as-prepared InOOH by XPS analysis. The resulting C,N-codoped InOOH exhibited much higher activity than undoped InOOH, P25, and C,N-codoped TiO2 on the photocatalytic degradation of RhB under visible light irradiation. This work not only deepens understanding of the morphology evolution and C,N-codoping processes of InOOH microspheres, but also provides new insight on the doping effects of C and N for visible light photocatalysis.