Ion oxide nanoparticles (IONPs) were prepared in monoolein (MO) cubic phases. Cubic phases were prepared by hydrating molten MO with Fe2+/Fe3+ salt solutions of which concentrations were 0.0125 M/0.025 M, 0.00625 M/0.0125 M, and 0.003125 M/0.00625 M. When the concentration were greater than 0.0125 M/0.025 M, cubic phase were hardly formed possibly because MO can be readily oxidized at a high concentration of Fe3+. The Fe2+/Fe3+-loaded cubic phases were alkalized by adsorbing aqueous solutions of NaOH (0.1 M, 0.05 M, and 0.025 M) into the cubic phases for the co-precipitation of the ions within the cubic phases. The resulting IONPs were around 10 nm on TEM photos, and the concentration of ions had little effect on the sizes. And, the size was somewhat less than IONPs prepared in bulk phases, possibly because the co-precipitation of Fe2+/Fe3+ will take place in the water channels of the cubic phases. The cubosomes containing IONPs were prepared by micronizing the cubic phases. Magnetic interaction between the cubosomes and a magnet were observed and the interaction was proportional to the amount of IONPs in the cubosomes.