Abstract: We report synthesis and crystal structure of a new copper molybdate oxosulfate Cu6O2(MoO4)3(SO4). The new compound is obtained in evacuated silica ampoules at 675-725 °C. Cu6O2(MoO4)3(SO4) is monoclinic, space group P21/m, a = 7.5208(4) Å, b = 6.8602(3) Å, c = 14.0019(7) Å, β = 93.471(5)°, V = 721.09(6) Å3, R1 = 0.051. The 3D framework of the new compound consists of oxo-centered [OCu3]4+ chains and MoO4 and SO4 tetrahedra. The structural motif of the new compound is related to the previously described fumarole minerals, glikinite Zn3O(SO4)2 and vergasovaite Cu3O(MoO4)(SO4). The crystal chemical peculiarities of this group of synthetic compounds and minerals are discussed