The title compound, trans-[Ru(bpy)(2)(H(2)O)(2)](CF(3)SO(3))(2) (bpy = 2,2'-bipyridine, C(10)H(8)N(2)), crystallized from the decomposition of an aged aqueous solution of a dimeric complex of cis-Ru(bpy)(2) in 0.1 M triflic acid. The Ru(II) ion is located on a crystallographic inversion center and exhibits a distorted octa-hedral coordination with equivalent ligands trans to each other. The Ru-O distance is 2.1053 (16) Å and the Ru-N distances are 2.0727 (17) and 2.0739 (17) Å. The bpy ligands are bent, due to inter-ligand steric inter-actions between H atoms of opposite pyridyl units across the Ru center. The crystal structure exhibits an extensive hydrogen-bonding network involving the water ligands and the trifluoromethane-sulfonate counter-ions within two-dimensional layers, although no close hydrogen-bond inter-actions exist between different layers.