Magnetic materials synthesized on the nanometer-scale level are essential for several applications, such as spintronics and magnetologic. As a successful nanofabrication approach, focused electron beam-induced deposition (FEBID) stands out as a direct-write technique. FEBID uses an electron beam to locally induce a CVD process, avoiding the use of masks and resists. In this work, Fe–based nanostructures are synthesized on Si(100) by FEBID, starting from iron pentacarbonyl. A systematic variation of FEBID parameters is performed, to study their influence on the geometry and composition of the deposit. Based on the results, specific deposition conditions are suggested for magneto-logic applications and fabrication of large structures.