Desorption rates of erucamide from erucamide/isotactic polypropylene (i-PP) blends were measured microgravimetrically under vacuum. Experimental data were used for testing our theoretical description of diffusion processes in the erucamide/i-PP system, a partially inhomogeneous binary and incompatible system, and for the calculation of the diffusion parameters. For films containing 4.6% and 8.0% erucamide, the kinetic curves show good agreement with the Fickian law. However, for films containing 24.0% and 44.0% erucamide, the experimental results were explained by assuming two terms for the overall transport process, a diffusional term which describes in the amorphous regions of spherulites, and a term describing the release from the globules to the amorphous region of spherulites. An equation was derived to describe our experimental data for these high erucamide content blends (24.0% and 44.0%).