Single crystals of [CH6N3]2[(UO2)2(SO4)3] (I) have been prepared by evaporation from 2 ml aqueous solution of uranyl nitrate, guanidine sulfate and sulfuric acid. The unit cell parameters were determined by the least squares method. Compound I has a monoclinic symmetry [s.g. P21212, a=9.907(3) Å, b=9.597(3) Å, c=9.762(3) Å, V=928.2(5) Å3, Z = 2]. The crystal structure have been solved by the direct methods from X-ray diffraction data and refined by the least-squares techniques to R1 = 0.025 (wR2 = 0.057) for 2066 reflections with |Fo| ≥ 4σF.