PtTl3 crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Pt is bonded to twelve equivalent Tl atoms to form a mixture of edge and face-sharing PtTl12 cuboctahedra. All Pt–Tl bond lengths are 3.30 Å. Tl is bonded in a 6-coordinate geometry to four equivalent Pt and two equivalent Tl atoms. Both Tl–Tl bond lengths are 2.96 Å.