The interfacial charge carrier dynamics of the three-component semiconductor-semiconductor-metal heterojunction system were investigated and presented for the first time. The samples were prepared by selectively depositing Pt nanoparticles on the TiO 2 surface of In 2O 3-decorated TiO 2 nanobelts (In 2O 3-TiO 2 nanobelts (NBs)) using the typical photodeposition method. For In 2O 3-TiO 2 NBs, because of the difference in band structures between In 2O 3 and TiO 2, the photoexcited electrons of In 2O 3 nanocrystals would preferentially transfer to TiO 2 NBs to cause charge carrier separation. With the introduction of Pt on TiO 2 surface, a fluent electron transfer from In 2O 3, through TiO 2, and eventually to Pt was achieved, giving rise to the increasingly pronounced charge separation property for the as-prepared In 2O 3-TiO 2-Pt NBs. The remarkable charge separation of the samples was revealed with the corresponding photocurrent measurements. Time-resolved photoluminescence spectra were measured to quantitatively analyze the electron transfer event between In 2O 3 and TiO 2 for In 2O 3-TiO 2 NBs and its dependence on Pt deposition. Upon the deposition of Pt, In 2O 3-TiO 2 NBs showed an increased apparent electron-scavenging rate constant, fundamentally consistent with the result of their performance evaluation in photocatalysis. The current study provides a new paradigm for designing highly efficient three-component nanoheterojunction photocatalysts which can effectively produce chemical energy from absorbing light.