The formation of iron oxide nanoparticles within the sodalite cages and supercages of Y zeolites was investigated. The zeolite was stirred in solutions of ferric nitrate at different concentrations to exchange the original Na ions with Fe(III) ions. Various oxidizing agents were used to accelerate the formation of iron oxide. X-ray fluorescence (XRF) results indicated that almost all Na ions were completely exchanged. Density comparisons of the original zeolite and the zeolite-Fe(III) powders indicated an increase in density of the latter, due to iron uptake. X-ray diffraction (XRD) results showed that the crystallinity of the zeolite matrix was destroyed at high concentrations of Fe(III) solution. At lower concentrations of Fe(III) solution, the zeolite matrix was retained but the precipitated iron oxide was too small to be detected. Scanning electron microscopy (SEM) images of the precipitated zeolite-Fe(III) specimens showed no observable particles on the external surfaces of the zeolites, indicating that iron oxide nanoparticles were formed within the zeolite matrix.