The mixed-metal title compound, BaCu_1/3Ta_2/3S₃ [barium copper(II) tantalum(V) trisulfide], was prepared through solid-state reactions. The crystal structure adopts the BaTaS₃ structure type and consists of face-sharing [MS₆] (M = Ta,Cu) octahedra (point-group symmetry -3m.) that are condensed into infinite chains along [001]. Adjacent chains are linked through the barium cations (site symmetry -6m2), which exhibit a coordination number of twelve. The M site is occupied by 2/3 of Ta^V and 1/3 of Cu^II, whereby the average M—S distances are slightly longer than those of ordered BaTaS₃. The classical charge balance of the title compound can be represented by [Ba²⁺] [(Ta/Cu)⁴⁺] [S²⁻]₃.