A process for the additivation of synthetic fibers, artificial fibers and polymers conferring special properties to them, the process comprising the following steps: the encapsulation of an additive in the pores of a porous material; the incorporation of particles of the porous material (capsules) into the polymer matrix of the fiber; and spinning of the fiber; the capsule withstanding the temperatures and other conditions of the different manufacturing processes which the fibers might undergo and the introduction of the additive into the polymer matrix thereof, characterised in that the porous material is a metal oxide, a zeolite, an aluminophosphate, clay, a carbon material, a hybrid organic-inorganic material or a porous polymer. The invention is an improvement in the additivation process of fibers and polymers in terms of the nature of the capsules used, the increase in the storage capacity of additives thereof, the process of incorporating the capsules into the polymer matrix of the fibers and the fact that the present invention refers to an industrial process.