The new Ag₂Ti₂P₂S₁₁ quaternary phosphosulfide disilver dititanium undecathiodiphosphate is obtained by heating the elements at ca 850 K in an evacuated silica tube. It crystallizes in orthorhombic symmetry, Pnma space group, with a = 8.5222 (11), b = 6.8359 (10), c = 24.142 (4) Å, V = 1406.4 (4) ų and Z = 4 at 293 K. The refinement of the room-temperature structure leads to a reliability factor of R = 0.0378 for 1556 independent reflections and 128 variables. Ag₂Ti₂P₂S₁₁ is composed of layers, separated by van der Waals gaps. The layers are composed of [Ti₂S₉] chains built from [TiS₇] units (TiS₆ octahedra in which a corner has been replaced by an S₂ pair) and linked through regular [PS₄] and highly distorted [AgS₄] tetrahedra. The formula of the compound can be written as Ag^I ₂Ti^IV ₂P^V ₂(S₂)^−IIS^−II ₉. A Gram–Charlier anharmonic development of the atomic displacement factor for Ag atoms reveals a strong non-harmonic probability density deformation, especially in the direction of two empty neighbouring tetrahedra, away from the Ti and P cations. The temperature dependence of the effective one-particle potential shows that the Ag distribution is primarily static in nature. At high temperature the tetrahedrally coordinated site is the preferential site. At lower temperature the Ag atoms are redistributed over the tetrahedral site and the adjacent triangular site. The disorder could not be resolved due to a phase transition with splitting of spots just below room temperature.