Thin silica films embedded with Au nanoparticles (NPs) were prepared by atom beam co-sputtering and RF-magnetron sputtering. The growth kinetics of Au NPs in atom beam co-sputtered film, under 90 MeV Ni ion irradiation, was studied by in-situ X ray diffraction experiment in the materials science beam line at IUAC, New Delhi. The growth of NPs from 4 nm (for pristine) to 9 nm at a fluence of 1 × 1014 ions/cm2 was observed with rapid growth upto the size track diameter, however slowed beyond it. 120 MeV Au ion irradiation of RF magnetron sputtered films resulted in the elongation of Au NPs along ion beam direction. The aspect ratio of elongated NPs (Au nanorods) is found to be ∼3.5, which mainly depends on the electronic energy deposited within the system. Hence the present work reports that the ion irradiation is an effective tool for tailoring the size, shape and size distribution of NPs. The results are discussed in the framework of thermal spike model.