Rb2CoS2 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional. Rb1+ is bonded in a 6-coordinate geometry to six equivalent S2- atoms. There are a spread of Rb–S bond distances ranging from 3.33–3.64 Å. Co2+ is bonded to four equivalent S2- atoms to form edge-sharing CoS4 tetrahedra. All Co–S bond lengths are 2.32 Å. S2- is bonded in a 2-coordinate geometry to six equivalent Rb1+ and two equivalent Co2+ atoms.