The perovskite-type solid solution LaSr(Ni1-xCux)TaO6 was synthesized and characterized by powder X-ray diffraction and iodometric titration. The stoichiometric solid solutions were synthesized at 1050-1100°C in air. The compounds for 0≤x≤0.6 have the (NH4)3FeF6-type structure with ordering between (Ni2+, Cu2+) and Ta5+. Tetragonal distorted (NH4)3FeF6-type phases due to the Jahn-Teller effect formed in the compositional range, x≥0.7 and the monoclinic distortion was observed for x=0.9 and 1.0. This result suggests that the tetragonal distortion occurs when the amount of Cu2+ becomes more than 35% of the octahedral site in this system.