The adsorption of polyelectrolytes onto plasma-pretreated poly(tetrafluoroethylene) (PTFE) surfaces is reported as a method for fluoropolymer surface modification. PTFE was treated in oxygen or ammonia plasmas in order to introduce oxygen-containing and nitrogen-containing groups, respectively, which increase the surface free energy and make possible the adsorption of polyelectrolytes via electrostatic interactions. We investigated the adsorption of poly(diallyldimethylammonium chloride) and poly(sodium styrenesulfonate) on the plasma-pretreated PTFE. The modification effects were evaluated by means of contact angle and streaming potential measurements.