Crystals of monoclinic Cu2SnS3 have been prepared by a conventional solid-state reaction. The crystal structure has been refined from a twinned specimen using X-ray diffraction data collected with an automatic diffractometer applying a high-dimensional twin refinement technique: space group Cc, a = 6.653(1), b = 11.537(2), c = 6.665(1) Angstrom, beta = 109.39(3)degrees Z = 4, R-F 0.036, and wR(F) = 0.038 for 1237 reflections and 52 structural parameters. The structure is a superstructure of the sphalerite type structure, based on cubic close packing of S with order arrangement of Cu and Sn in tetrahedral sites, and it is isomorphic with Cu2GeS3 and Cu2SiS3.