In this study, firstly, N-(hydroxymethyl) acrylamide (HMAAm) was grafted on poly(ethylene terephthalate) fibers (PET) by utilizing benzoyl peroxide (Bz(2)O(2)) as an initiator. The alteration in graft percentage with the polymerization time, temperature, concentration of initiator and monomers were investigated. For grafting experiments, the optimum temperature, duration for grafting and initiator concentration were found be 85 degrees C, 4 h and 0.008 M, respectively, and the maximum grafting yield was determined to be 25% at these conditions. After grafting, the morphological and chemical changes on the grafted fibers were examined scanning electron microscopy and Fourier-transform infrared spectroscopy. The thermal properties of the obtained PET fibers were examined with differential scanning calorimeter analysis. In addition, the water absorption capacities of the grafted fibers obtained at optimal conditions were investigated and it was found the maximum percentage of water retention reached 56%. Removal of Congo red (CR) with the grafted fibers was performed using a batch process. The effects of different parameters such as pH, grafting yield of HMAAm, adsorption time and CR concentration on the sorption capacity of the grafted fibers were investigated. The optimal pH for adsorption of CR was found to be 2, and the adsorption process reached equilibrium in 4 h. The amount of adsorbed CR molecules increased with the increment in the grafting yield up to 17%, and the graft copolymers adsorbed CR with 5.62 mg/g efficiency when the initial CR concentration was 80 ppm. The PET-g-HMAAm fibers synthesized in this study can be obtained easily and inexpensively, and the constructed fibers could be used to remove ionic substance from aqueous solution.