The compound [(CH 3 ) 4 N] 2 Ge 4 MnS 1 0 has been synthesized hydrothermally in glass ampoules at 393 K for two days. It has been investigated by means of X-ray diffraction and thermogravimetry. It crystallizes with the tetragonal symmetry, space group I4 and unit cell parameters, α = 9.5058(6) and c = 14.190(2) (Z = 2). The crystal structure was determined ab initio from conventional X-ray powder diffraction data and refined by the Rietveld method (R F = 0.046, R w p = 0.071). The structure of [(CH 3 ) 4 N] 2 Ge 4 MnS 1 0 consists of tetrahedra sharing apices with a space filling of the (Ge, Mn)S framework close to 45% (8 tetrahedra (1000 3 ) - 1 ) consistent with the low density of the material (ρ o b s = 2.10 g cm - 3 ). This thiogermanate exhibits tunnels with a mean diameter of 7 running along the [100] and [010] directions in which the (CH 3 ) 4 N + positive counterparts are located.