Durable antimicrobial acrilan fabrics were prepared by using cetylpyridinium chloride (CPC) in a chemical finishing process. The CPC could form ionic interactions with anionic groups on acrilan fibers, which contribute to durable antimicrobial functions. Reaction conditions such as pH, temperature, and time of the chemical treatment affected exhaustion of CPC and antimicrobial properties. However, the pH conditions of the finishing bath also impacted mechanical properties and color of the fabrics, particularly under alkaline conditions. Although a more alkaline condition is preferred for durable antimicrobial functions, high pH reduces tensile strength and results in yellowing of acrilan fibers. The yellowing of the acrilan fibers is caused by the hydrolysis of acrylonitrle groups and induced formation of conjugated C N systems in the polymers. The conjugated systems were characterized by FTIR.