Oxygenation reaction of cyclohexene was studied under the presence of a fourfold UO₂ ²⁺ complex with cyclohexyldiphenylphosphine oxide, [UO₂(OPCyPh₂)₄]²⁺, and blue light irradiation at 436 nm in acetonitrile. As a result, 1,6-hexanedial, cyclohexene oxide, 2-cyclohexen-1-one, and 2-cyclohexen-1-ol were photocatalytically generated as oxygenated products with turnover frequency = 6.7 h^–1. In contrast, dimerization of cyclohexene was observed under Ar atmosphere. This implies that a hydrogen atom at the allyl position is abstracted by photoexcited *[UO₂(OPCyPh₂)₄]²⁺ to give a cyclohexene radical and a U(V) intermediate [U^VO₂(OPCyPh₂)₄]⁺, being well supported by the density functional theory calculation. Under an O₂ atmosphere, the former reacts with dissolved O₂ to give 2-cyclohexen-1-one and 2-cyclohexen-1-ol. Dissolved O₂ would be activated by the U(V) intermediate to afford O₂ ^2– in the end, which drives oxygenation of the C=C bond of unreacted cyclohexene.