Cadmium sulfide (CdS) and cadmium selenide (CdSe) quantum dots (QDs) are sequentially loaded onto anodized TiO₂ nanotubes to fabricate a CdS/CdSe co-sensitized photoelectrode for visible light response. These QDs are loaded on TiO₂ nanotubes by polymer brushes assisted in situ formation, and they are distributed uniformly around both inner and outer walls of TiO₂ nanotubes. The interpenetrating polymer can provide a superior nano-confined environment and will prevent the nanoparticles from growing further during nucleation. More importantly, the potential advantage of using polymer brushes is the capability of tuning the loading amount of QDs via multiple cation exchange. The photoresponse of CdS/CdSe-TiO₂ nanotubes has been efficiently extended into the visible-light region, indicating potential applications in solar cell devices.