H2Ti4O9/Cd0.8Zn0.2S nanocomposites incorporating Cd0.8Zn0.2S particles, less than 1 nm in thickness, were fabricated by the chemical reaction between a Cd2+-Zn2+ mixture and H2S in the interlayer of H2Ti4O9. H Ti4O9/Cd0.8Zn0.2S nanocomposites were capable of efficient hydrogen evolution following irradiation with visible light in the presence of Na2S as a sacrificial donor. The hydrogen production activity of the H2Ti4O9/Cd0.8Zn0.2S nanocomposite was superior to those of unsupported Cd0.8Zn0.2S and the mixture of H2Ti4O9 and Cd0.8Zn0.2S. The hydrogen production was enhanced by doping Pt together with Cd0.8Zn0.2S in the interlayer, but was depressed by depositing Pt on the outer surface of the H2Ti4O9/Cd0.8Zn0.2S nanocomposite.