Wood is one of the key renewable resources due to its excellent structure and physical properties. Functionalized wood and wood-based materials not only possess important engineering applications but also great potential in some new technology fields, such as electronics, optics, and energy. Endowing these functional wood-based materials with magnetic properties has an important significance for exploring lightweight building materials or electronic devices. In this study, we report the fabrication of a transparent magnetic wood (TMW) based on filling the index-matching methyl methacrylate and magnetic Fe3O4 nanoparticles into the delignified wood template. The presence of the polymer and Fe3O4 nanoparticles within the wood structure is monitored by scanning electron microscopy, energy-dispersive X-ray analysis, and Fourier transformation infrared spectroscopy. The resulting TMW possesses moderate transparency and magnetic properties combining with outstanding mechanical performance. Moreover, the influence of the concentration of Fe3O4 nanoparticles on the final optical, magnetic, and mechanical properties of TMW is also discussed. This work provides a potential strategy to develop wood-based materials for magneto-optical application.