Currently, due to the rapid development of communication technology, electromagnetic interference (EMI) and irradiation have become an emerging environmental pollutant. Herein, hierarchical and porous structured wood is used as the lightweight three‐dimensional organic scaffold for the incorporation of magnetic iron oxide nanoparticles through an in situ mineralization process that endows the woodblock with favorable appearance as well as magnetic and EMI shielding properties. The two‐step process involves the removal of lignin from natural wood via cooking and bleaching followed by inorganic mineralization. The resultant magnetic wood displays an optical brown appearance and possesses a typical magnetic hysteresis behavior with a saturation magnetization of 4.5 emu g−1 for the whole wood. More importantly, the obtained magnetic wood is much lighter than traditional magnetic metal and construable for versatile applications. Notably, the 3 mm thick magnetic wood shows 5–10 dB (or 7–10×) enhanced electromagnetic wave attenuation across the X‐band of 8–12 GHz compared with nonmagnetic wood with the same thickness. The enhanced electromagnetic wave absorption of magnetic wood is mainly due to its enhanced magnetic loss tangent compared with nonmagnetic wood. This work provides an inspiring strategy to develop sustainable, lightweight, and environmentally friendly wood for multifunctional magnetic applications.