This study demonstrated a dye-sensitized TiO₂-polyoxometalate system (denoted TiO₂-(PW₁₂-TH)₈, where PW₁₂ = PW₁₂O₄₀³⁻ and TH = thionine) for selective oxidation of alcohols under visible light. The results showed that various substituted alcohols were transformed into their corresponding aldehydes with high selectivity. Due to more efficient electrons transfer, large surface area, and enhanced visible light absorption, the photocatalytic activity of TiO₂-(PW₁₂-TH)₈ was superior to any other dye-sensitized system reported to date. The response in the photocurrent-time curves over several on/off cycles of intermittent irradiation showed good reproducibility. The photocurrent response of TiO₂-(PW₁₂-TH)₈ was much higher than that of TiO₂/TH (physical mixture of TiO₂ and TH), SiO₂-(PW₁₂-TH)₈ or P25-(PW₁₂-TH)₈ (P25 = Degussa P25), attributed to the more efficient transfer and longer lifetime of photoexcited electrons. This photocatalytic process confirmed that efficient electron transfer during photocatalytic oxidation plays a vital role in determining the reaction conversion and obtaining good selectivity. Electron paramagnetic resonance (EPR) spectra and radical scavenging experiments proved that superoxide radicals and electrons were the main reactive species in the proposed system, the absence of hydroxyl radicals and holes is demonstrated to be the key of high reaction selectivity.