The kinetics of the tetraethylammonium ion transfer from water to o-nitrophenyl octyl ether has been studied by impedance measurements at the equilibrium cell potential. Enhanced capacity of the interface points to a significant specific adsorption of the tetraethylammonium ion, probably via forming the interfacial ion pairs. In spite of the coupling between the ion transfer and the ion adsorption, a non-linear least squares fitting of impedance data to the Randles-type equivalent circuit or to an impedance model accounting for the specific ion adsorption yields similar values of the kinetic parameters. The most important finding is that the ratio of the rate constants of the tetraethylammonium ion transfer from water to nitrobenzene and to o-nitrophenyl octyl ether correlates with the inverse ratio of the organic solvent viscosities. The low viscosity of 1,2-dichloroethane can then be responsible for rather fast ion transfer kinetics at the water1,2-dichloroethane interface. The viscosity effect is likely to be associated with the friction exerted by the organic solvent molecules on the hydrated ion penetrating the organic solvent to some depth prior to the ion transfer step.