The large surface inertness of polyethylene terephthalate (PET) fibers and fabrics presented numerous scientific and technical challenges in overcoming problems due to the PET’s disadvantageous properties such as less wearing comfort, limitation in coloration properties, buildup of electrostatic charges, insufficient soil release, and poor washability. However, the PET surface inertness has constrained the use of PET fabrics for further application in garments and other industries. Surface modification seem to be an attractive tool toward this objective it guarantees maintenance of key bulk properties. Plasma-based surface modifications offer many interesting possibilities for the production of high value-added polymeric materials. In this work, plasma-based synthetic concept was employed to endow PET fabrics with quaternary ammonium group that can be used for the subsequent immobilization of anionic molecules. The PET fabric surface was modified by low-pressure oxygen (O) plasma in order to introduce O-containing functional groups such as carboxylic groups. These carboxylic groups can act as an anchor for the adsorption of poly(diallyldimethylammonium chloride) from an aqueous solution to PET fabric surface. The modified surfaces were characterized by a combination of various surface-sensitive techniques.