A diselenido-bridged dinuclear ruthenium complex, [{RuCl(P(OMe)(3))(2)}(2)(mu-Se-2)(mu-Cl)(2)] was synthesized by the reaction of trans-[RuCl2 (P(OMe)(3)}(4)] and red amorphous selenium. A single crystal X-ray structure analysis showed that the topological geometry was the same as that of the disulfido analogue. The Ru-Se and Se-Se lengths are longer than the corresponding ones in the disulfido analogue according to the difference between the covalent radii of sulfur and selenium. Electrochemical measurement indicated that the title complex undergoes electrical reduction and subsequent chemical reaction.