PET fibers was treated by means of NH₃ plasma in order to improve the adhesion between PET fiber and PP/NBR TPE, which was compatibilized with GMA-PP. The adhesion between the surface modified PET fiber and PP/NBR TPE was markedly improved (~ 60%), as measured by the pull-out test. Surface of plasma treated PET fiber was characterized by ATR-IR and XPS. The existence of any residue of matrix rubber on the PET fiber surface after pull-out test was examined by scanning electron microscope (SEM). The enhancement of the adhesion between PP/NBR matrix and plasma-treated PET fibers is due to the formation of functional groups on the fiber surface and the surface roughening of the fiber by sputtering effect.