The MW-assisted synthesis of materials is a recent and a novel method. This chapter discusses the microwave-assisted synthesis of technologically important materials, such as functionally graded (FG) tungsten copper for future reactors, nanocrystalline ferrite (Fe3O4) for targeted drug delivery, magnetic nanocomposites for groundwater remediation, microwave-assisted synthesis of glass for NIR shielding, and glass ceramic for nuclear waste immobilization. The H-field of microwave radiation at microwave frequency (2.45 GHz) is utilized for phase transformation/decrystallization of M-type hard barium hexaferrite (from crystalline to amorphous). The decrystallized hexaferrites are found to be good alternative RE-free permanent magnet.