Aromatic polysulfonamide fibers (PSA) are impossible to be dyed with conventional dyeing techniques because of their extremely high glass transition temperature (Tg 280 similar to 380 degrees C). To make the PSA fibers dyeable without a carrier under normal pressure, PSA fibers were grafted using gamma-ray irradiation with acrylic acid (AA) as a monomer. In addition to the dyeability, changes in other inherent performance characteristics of PSA fibers after irradiation grafting were evaluated, such as the mechanical behavior, thermal stability, hygroscopicity, and flame retardancy. Meanwhile, the effect of irradiation grafting on the performance of PSA fibers was revealed using structure information in different length scales. The results showed the AA-grafting copolymerization occurred not only on the surface of PSA fibers, but also in the amorphous region within the fibers. The polyacrylic acid grafted chains could act as an internal plasticizer, enlarging the free volume of fibers, which make the PSA fibers dyeable with a cationic dye and disperse dye. The color fastness of the dyed PSA fibers was strongly reliant on the dye category. The irradiation-grafting treatment has little adverse effect on the inherent performance of PSA fibers such as mechanical properties, thermal stability and flame retardancy within a proper grafting yield. POLYM. ENG. SCI., 59:592-601, 2019. (c) 2018 Society of Plastics Engineers