Grafting of 2-hydroxyethyl methacrylate (HEMA) on poly(ethylene terephthalate) (PET) fibers was carried out via free-radical polymerization technique using benzoyl peroxide as initiator. The obtained copolymers were examined by scanning electron microscope and Fourier-transform infrared spectroscopy analysis, and it was proved that HEMA was successfully grafted onto the PET structure. The synthesized fibrous adsorbents were used to remove Congo red (CR) from aqueous solutions by batch adsorption method. The effects of pH, grafting yield, operation time and dye concentration were studied to find optimal conditions for adsorption of CR by the HEMA-grafted PET (PET-g-HEMA). The obtained results showed that the amounts of adsorbed dye on the PET-g-HEMA lowered with increasing pH. At pH 2, the dye amount adsorbed by the fibers increased with increasing dye concentration up to 70 ppm and grafting yield up to 110%. It was also seen that the adsorption had considerably rapid kinetic and achieved equilibrium within 60 min. The maximum removing abilities of the grafted fibers was found to be 16 mg/g when the beginning concentration of CR was 70 ppm at pH 2. The dye was desorbed from the loaded fibers with 1 M NaOH solution, and it was found that 83% of the adsorbed dye was recovered. The investigations on reusability of the PET-g-HEMA fibers showed that the constructed fibers can be used at least five times without losing adsorption capacities for CR. All these results indicate that the grafting can be used to remove the anionic dyes from the aqueous solution.