A new mixed-cluster molybdenum sulfide Cs4[Mo3S(S2)6][Mo3S(S2)5(S4)]-0.5H2O was synthesized by the hydrothermal method and characterized by single-crystal X-ray diffraction. The compound consists of distinct layers of two types of molybdenum sulfide clusters : type A, [Mo3(mu3-S)(S2)6]2-; type B, [Mo3(mu3-S)(S2)5(S4)]2-. The type B clusters are linked in one-dimensional chains through weak S-S intercluster interactions.