Single crystals of (C3H8N6)[(UO2)2(SO4)3(H2O)](H2O) were obtained by evaporation from aqueous solution at room temperature conditions. Novel compound crystalizes in monoclinic system [S.G. P21/n, a = 11.1194(4) Å, b = 10.5921(3) Å, c = 17.0143(6) Å, b = 101.405(2) o, V = 1964.34(11) Å3, Z = 4, R1 = 0.024]. Structure is based on the [(UO2)2(SO4)3(H2O)]2– layers, built up with corner shared uranium and selenium coordination polyhedra. Negative charge of the inorganic layers is compensated by protonated melamine molecules (C3H8N6)2+.