Functional agent-containing fibers according to an embodiment of the present invention, wherein a functional agent is supported by silicone fixed to the fibers. The silicone includes an acrylic-modified organopolysiloxane having two or more acrylic groups per molecule. A rate of decrease in the functional agent after the functional agent-containing fibers are washed 10 times is less than 40%. In the present invention, the functional agent-containing fibers may be produced, e.g., by irradiating fibers impregnated with a fiber treatment agent A containing silicone with an electron beam so that the silicone is fixed to the fibers, and impregnating the fibers to which the silicone has been fixed with a fiber treatment agent B containing a functional agent. The functional agent-containing fibers may be produced, e.g., by impregnating fibers with a fiber treatment agent C containing silicone and a functional agent and irradiating the fibers impregnated with the fiber treatment agent C with an electron beam so that the silicone is fixed to the fibers and the functional agent is supported by the silicone fixed to the fibers. Thus, functional agent-containing fibers having improved washing resistance and a method for producing the fibers are provided.