Spherical silica particles doped with iron oxide have been synthesized via base-catalyzed one-pot sol–gel process using tetraethoxysilane (TEOS) and iron(III) eth- oxide (ITE) as co-precursors. In the modified Sto ̈ ber pro- cess adopted, depending on the concentration of ITE in the starting composition, materials of various morphologies were observed under a scanning electron microscope and an atomic force microscope. The presence of ITE signifi- cantly affected the formation process of particulate silica; the spherical particles were formed accompanied by the co- presence of irregular-shaped finer aggregates. The fraction of the aggregates with rough surfaces increased with an increase of the ITE content in the reaction mixture. Both the spherical particles and irregular-shaped aggregates contained iron hydroxide and they exhibited paramagnetic behavior. The chemical composition and physicochemical properties of the materials were determined using various complementary spectroscopic methods.