Silica coated mesoporous Fe (Fe@SiO2) microcubes were designed for high performance electromagnetic wave attenuation. Silica coating lowered the permittivity significantly over the bare Fe cubes. Most importantly, silica coating was able to keep the shape of iron particles as well as to ensure a mesoporous structure. The synthetic approach consists of three steps. α-Fe2O3 microcubes were firstly synthesized by a hydrothermal method. Then, the cubes were coated with silica. The silica coated α-Fe2O3 microcubes were finally reduced under hydrogen gas at 500 oC. The reduction of iron oxide resulted in a removal of oxygen atoms and subsequently left the empty space as pores inside of silica coated iron cubes. The silicon resin composites containing Fe@SiO2 microcubes exhibited impressive electromagnetic wave attenuation characteristics. The reflection loss value of – 54 dB could be obtained at 3.2 GHz with a thickness of 4.5 mm. In addition, the mesoporous characteristic offered a low density of Fe@SiO2 mesoporous microcubes. The microcubes enabled a RL of – 15 dB with a film thickness as thin as 3 mm. The silica coated mesoporous iron microcubes significantly reduced the usage/thickness of silicon resin composite. They are very promising as a strong-attenuation and light-weight electromagnetic wave attenuation material.