A computer‐simulated model for the fatigue behavior of multifilamentary unidirectional composites is presented. It is applicable to two‐component composites with perfectly elastic filaments in a ductile matrix, and considers both applied cyclic stresses and strains. Information regarding the change in residual stress state, matrix yield strength, and the number of cycles necessary to stabilize properties by the achievement of totally elastic strains (shakedown), or to reach some preassigned failure stress in the matrix, can be determined. Results obtained are applied directly to the fatigue behavior of multifilamentary Nb3Sn superconducting composites.