We have studied Fe films on Ar + ion sputtered highly oriented pyrolitic graphite (HOPG) using scanning tunnelling microscopy (STM). The adsorbed Fe atoms form nanoparticles uniformly distributed over the substrate surface with narrow size distribution. Comparing these data with Fe deposited on non-sputtered HOPG indicates the role of substrate defects, acting as nucleation sites, on the overall film structure. However, the shape and size of individual defects do not seem to influence the shape of the nanoparticles. The correlation between the Fe film morphology and the sputtered substrate morphology is discussed taking into account the different capturing properties of sputtering-induced defects.