A novel catalyst, consisting of hollow silica-coated porous carbon with embedded iron oxide particles (FeO_x@C/SiO₂), was synthesized by the extended Stöber method. Iron ions were incorporated in a resorcinol–formaldehyde resin in the presence of citric acid to form a template, which was then coated with a silica layer. The iron oxide-embedded porous carbon and hollow silica were simultaneously formed during calcination under N₂ atmosphere. Through this process, silica endowed the iron oxide with low crystallinity and small size, resulting in a higher catalytic activity in the heterogeneous Fenton system for the decolorization of a methylene blue (MB) solution within 25 min. Moreover, the sample maintained 78.71% of its catalytic activity after three cycles.