Tl3TaS4 crystallizes in the cubic I-43m space group. The structure is three-dimensional and consists of two Tl3TaS4 frameworks. Ta5+ is bonded in a tetrahedral geometry to four equivalent S2- atoms. All Ta–S bond lengths are 2.29 Å. Tl1+ is bonded in a 12-coordinate geometry to four equivalent S2- atoms. All Tl–S bond lengths are 3.20 Å. S2- is bonded in a distorted single-bond geometry to one Ta5+ and three equivalent Tl1+ atoms.