Application of Fe3O4 nanoparticles (NPs) as a robust, very efficient, and magnetically recoverable catalyst was investigated in Friedel-Crafts acylation (FCA) of ferrocene and aromatic compounds. This reaction was performed with acid chlorides in solvent-free conditions at room temperature. The catalyst was easily separated by an external magnetic field from the reaction mixture. The separated catalyst was recycled for several consecutive runs without appreciable loss of its catalytic activity.