In the present work, europium oxide was successfully developed as a newly active photocatalyst and used for H-2 evolution with Eosin Y (EY)-sensitized photocatalytic water splitting under visible light irradiation. A series of Pt nanoclusters (NCs) deposited on europium oxide photocatalysts was fabricated by an in-situ chemical deposition method. Electrochemical analysis showed that the conduction band potential of Eu2O3 was -0.82 V (vs NHE), which was more negative than the reduction potential of H2O/H-2. High-resolution transmission electron microscopy revealed that the Pt NCs had excellent dispersion and ultrasmall size (similar to 1.81 nm). The optimal photocatalytic H-2 evolution activity could be obtained by EY-sensitized 5 wt% Pt/Eu under visible light and reached 807.4 mu mol in 2 h. In addition, a reasonable mechanism for the enhancing photocatalytic H-2 evolution activity has been investigated and presented. This research indicates that lanthanide oxides with dye sensitization could be very promising photocatalysts for the reduction of water to H-2.