Carbon dots-TiO2 nanosheets (CDs-TNs) composites were synthesized by hydrothermal method and applied for the first time in photoreduction of Cr(VI) under sunlight illumination. The materials were characterized by transmission electron microscope, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectrometer, and X-ray photoelectron spectroscopy analysis. The results confirmed that CDs are successfully incorporated with TNs through Ti-O-C bonds. With the introduction of CDs, CDs-TNs composites exhibit excellent photoreduction performance of Cr(VI), which is higher than that of TNs, P25 and CDs-P25. The unique upconversion property and electron transfer property of CDs play essential roles on light harvesting and charge carriers transferring in the photoreduction process. Most importantly, CDs could facilitate the formation of H2O2, leading to the consumption of holes. As a result, the recombination of photoinduced electron-hole pairs is hindered and photoreduction activity of CDs-TNs is promoted.