The generation mechanism for intermodulation products in thin ferromagnetic resonators is examined. A sketch of classical theory provides a physical picture of this mechanism. Using this theory as a base, the effect of spin‐wave scattering on intermodulation is then predicted by treating the resonant mode and spin waves as magnons; spin‐wave scattering is found theoretically to increase the intermodulation products. A comparison of the full theory with experimental results on bandpass filters made with thin YIG resonators shows good agreement.