The complexation of two hydroxyethylcellulose, of different molecular weights, SC230 and SC240, with the anionic surfactants perfluorodecanoic acid, PFDA, and perfluorooctanoic acid, PFOA, has been studied. For this purpose, the anions transfer current across a water/1,2-dichloroethane interface was employed to quantify PFDA and PFOA concentration in the absence or in the presence of the polyelectrolyte. When polymers were added in increasing amounts to solutions containing PFDA or PFOA, a gradual decrease in current values was observed, evincing the binding of the anions to the polymer. Peak Current values for the transfer, were used for the drawing up the binding isotherms, which were fitted by Satake and Yang theory. Cooperative binding was observed, but all fluorinated acids gave a similar cooperativity parameter, and it was found that both the overall constant as well as the cooperative binding process, increases with the molecular weight of the polymer.