The quaternary title compound, caesium chromium(III) hepta-thio-diphosphate(V), CsCrP(2)S(7), has been synthesized using the reactive halide flux method. It is isotypic with other AMP(2)S(7) (A = alkali metal; M = Cr, V or In) structures and consists of two-dimensional (∞) (2)[CrP(2)S(7)](-) layers extending parallel to (001) which are separated from each other by Cs(+) ions (symmetry 2). The layer is built up from slightly distorted octa-hedral [CrS(6)] units (symmetry 2) and bent [P(2)S(7)] units consisting of two corner-sharing [PS(4)] tetra-hedra. The [CrS(6)] octa-hedra share two edges and two corners with the [PS(4)] tetra-hedra. There are only van der Waals inter-actions present between the layers. The Cs(+) ions are located in this van der Waals gap and stabilize the structure through weak ionic inter-actions. The classical charge balance of the title compound can be expressed as [Cs(+)][Cr(3+)][P(5+)](2)[S(2-)](7.).