Sengon (Falcataria moluccana Miq.) tree offers a wood of low quality and durability owing to its low density and thin cell walls. This study aimed to improve the properties of sengon wood by making the wood magnetic, producing new functions, and characterizing magnetic sengon wood. Each wood sample was treated using one of the following impregnation solutions: Untreated, 7.5% nano magnetite-furfuryl alcohol (Fe3O4-FA), 10% nano Fe3O4-FA, and 12.5% nano Fe3O4-FA. The impregnation process began with vacuum treatment at 0.5 bar for 2 h, followed by applying a pressure of 1 bar for 2 h. The samples were then tested for dimensional stability and density and characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM–EDX), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) analysis, and vibrating sample magnetometry (VSM) analysis. The results showed that the Fe3O4-FA impregnation treatment considerable affected the dimensional stability, measured in terms of weight percent gain, anti-swelling efficiency, water uptake, and bulking effect, as well as the density of sengon wood. Changes in wood morphology were detected by the presence of Fe deposits in the cell walls and cell cavities of the wood using SEM–EDX analysis. XRD and FTIR analyses showed the appearance of magnetite peaks in the diffractogram and Fe-O functional groups. Based on the VSM analysis, treated sengon wood is classified as a superparamagnetic material with soft magnetic properties. Overall, 10% Fe3O4-FA treatment led to the highest increase in dimensional stability and density of sengon wood.