Abstract The crystal structure of the binuclear copper(II) complex with 2-[2-(2-pyridyl)ethylthio] ethanol, Cu(py-3·2-nso)NO 3· 1 2 H 2O (where Hpy-3·2-nso denotes 2-[2-(2-pyridyl)ethylthio] ethanol) was determined by the single-crystal X-ray diffraction method. The crystals are triclinic, space group P 1 , a = 11.234(2), b = 15.605(2), c = 8.535(2) Å; α = 95.13(2), gb = 121.74(1), γ = 72.90(1)°. The structure was solved by the heavy atom method and refined by the block-diagonal least-squares method to an R factor of 0.043. The crystal consists of two crystallographically independent binuclear units. In both units, the coordination around the copper atom is a distorted square pyramid with two alkoxo oxygen, thioether sulfur and pyridine nitrogen atoms in the basal plane and an oxygen atom of nitrate ion or water molecule in the apical position. The magnetic property was discussed in terms of the structure, especially the conformation of the chelate ring.