This short communication reveals that the magnetic and porous properties of Fe-included single-walled carbon nanohorns (Fe-SWCNHs) can be improved via oxidation in water by injection of ozone at room temperature. Fe in Fe-SWCNHs is converted to ferrimagnetic Fe3O4 without producing paramagnetic Fe2O3 by this method. The specific surface area on the basis of the specimen mass can be doubled by this treatment together with significant increase of micro and meso pore volumes. Their magnetic susceptibility which is a determinant factor to magnetically drive the products in fluid can be increased by this ozone oxidation. The enhancement effects on the porous and magnetic properties of Fe-SWCNHs should be preferable to develop catalyst support or adsorption media which can be magnetically handled. The method proposed here is extremely safe and environmentally benign. (C) 2015 Elsevier B.V. All rights reserved.