Suitable single crystals of the title compound, barium dicobalt(II) bis-[orthoarsenate(V)], were prepared under hydro-thermal conditions. This phase belongs to a series of compounds with general formula AM(2)(XO(4))(2), where A = alkaline earth metal, M = Mg or a divalent first-row transition element, and X = P, As or V. BaCo(2)(AsO(4))(2) is isotypic with BaNi(2)(XO(4))(2) (X = P, V or As) and is characterized by brucite-like sheets of edge-sharing CoO(6) octa-hedra (3 symmetry) parallel to (001), with one-third of the octa-hedral positions being vacant. The sheets are capped above and below by AsO(4) tetra-hedra (3 symmetry) and are inter-connected by distorted BaO(12) cubocta-hedra ( symmetry).