A hybrid uranium iron cage nanoduster,[(UO2)(24) (Fe0H)(24) (0(2))(24) (PO4)(8) (CH(COO)(PO3)(2))(24)](96-) (U24Fe24), was synthesized using bridging ligands containing bisphosphonate and carboxylate groups. U24Fe24 contains six tetramers of uranyl hexagonal bipyramids and eight iron trimers, each of which consists of three corner-sharing Fe3+ octahedra and is stabilized by in situ formed phosphate and 2,2-bis(phosphonato)acetate (C2P2) groups. Tetramers and trimers are bridged by 24 C2P2 groups into a cage cluster. Crystals of U24Fe24 present a paramagnetic-like behavior. X-ray scattering showed that U24Fe24 forms in the reactant solution prior to crystallization and is stable upon dissolution in water.