© 2020 Elsevier B.V. Iron-based nanoparticles show unique magnetic properties, and their syntheses from metal complex solution by pulsed lasers have been widely studied; however, the aggregation of nanoparticles is unavoidable in homogeneous solution. We report the production of water-dispersible iron-based nanoparticles in a mixture of water and ferrocene n-hexane solution by femtosecond laser irradiation without using any additive agents. The mean diameter of iron-based nanoparticles (ca. 7 nm) is independent on the concentration of ferrocene and laser irradiation time. We propose that hexane microdroplets dispersed in water act as reaction vessels and reduce the opportunity of aggregation of primary nanoparticles.