In the title salt, [Ni(C 26 H 24 P 2 ) 2 ](CF 3 SO 3 ) 2 or [Ni(dppe) 2 ] 2+ ·(OTf − ) 2 [dppe = 1,2-bis(diphenylphosphanyl)ethane and OTf − = trifluoromethanesulfonate], the Ni atom (site symmetry \overline{1}) has a square-planar geometry with the bidentate ligands chelating the metal. As a result of the steric hindrance of the phenyl rings, the counter-ions are blocked from the metal coordination sphere. The dynamic disorder of the anion existing at 296 K is reduced at 100 K and based on these two temperatures, negative thermal expansion behaviour is observed.