A new nickel tellurite oxohalide, Ni(15)Te(12)O(34)Cl(10), has been prepared by chemical vapour transport reactions and the crystal structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P1[combining macron] with the pseudomonoclinic cell parameters a = 10.3248(6) Å, b = 10.3249(6) Å, c = 11.6460(8) Å, α = 73.782(6)°, β = 73.782(6)°, γ = 63.51(2)°, Z = 1, R(1) = 0.0264. The Ni(2+) ions have octahedral [NiO(6)] and [NiO(4)Cl(2)] coordinations, the Te(4+) ions have one-sided [TeO(3)] and [TeO(4)] coordinations. The crystal structure can be described as consisting of nickel oxide ribbons extending along (001) that are connected by corner sharing [TeO(3)] and [TeO(4)] groups to build the open framework structure. The chlorine atoms and the Te-lone pairs are facing voids in the oxide framework. The new compound undergoes two successive antiferromagnetic ordering transitions at ∼50 K and ∼10 K. The Curie-Weiss temperature obtained from detailed evaluation of the high-temperature magnetic susceptibilities is positive indicating predominant ferromagnetic superexchange interactions between the Ni magnetic moments.