The first entirely pentavalent uranium borate, Na-2(UO2)(BO3), was synthesized under mild hydrothermal conditions. The single-crystal structure was solved in the orthorhombic space group Cmcm with a = 10.0472(3) A, b = 6.5942(2) A, and c = 6.9569(2) A. Magnetic susceptibility measurements revealed an anti-ferromagnetic transition at 12 K and an effective magnetic moment of 2.33 mu(B). Density functional theory calculations indicated dynamic stability of the structure above 0 K.