This paper deals with a study of the effect of Si(+) ion irradiation on a Co/Pt multilayer system irradiated at different temperatures. The as-deposited and irradiated samples have been characterized using x-ray reflectivity (XRR), x-ray diffraction (XRD) and the magneto-optical Kerr effect (MOKE). X-ray reflectivity shows clear intermixing at the interfaces. The x-ray diffraction pattern shows that Si(+) ion irradiation at higher temperatures results in the formation of the CoPt(3) fcc phase with a small fraction of L1(0) phase. The mixing process is discussed in terms of recoil displacements induced by energy transfers from ions.