Abstract Ca₂TWO₆ (T = Co, Ni) perovskites have been prepared in polycrystalline form by thermal treatment, in air, of previously decomposed citrate precursors. These materials have been studied by X-ray (XRD) and neutron powder diffraction (NPD) data. Our results show that these compounds crystallize, at room temperature, in the monoclinic space group P2₁/n. The two perovskites contain divalent T (T = Co, Ni) cations. The low temperature antiferromagnetic ordering has been followed from sequential NPD data. Peaks of magnetic origin appear at the NPD patterns below temperatures of T_N = 36 K and T_N = 56 K for the Co and Ni compounds, respectively. The magnetic structures are both defined by a propagation vector k = (1/2, 0, 1/2), and can be described as an array of ferromagnetic layers of Co(Ni) moments, perpendicular to the [101] directions, coupled antiferromagnetically.