A novel method for the crosslinking of acrylic fibers was devised, which uses disulfonyl azides as crosslinking agents. This is a fiber-finishing process in which 1,6-hexanedisulfonyl azide, 1,3-benzenedisulfonyl azide, 4,4-biphenyldisulfonyl azide, 1,5-naphthalenedisulfonyl azide, and 2,6-naphthalenedisulfonyl azide were applied to an acrylic fiber (Courtelle) and thermally treated to bring about crosslinking. A study was made of the mechanical and thermal properties of the crosslinked fibers and of the abrasion and Pilling performance of the associated fabrics. Crosslinking brought about significant improvements in the initial modulus, resistance to abrasion, Pilling performance, and thermal stability of the fibers.