628Following advanced developments in synthesis and characterization technology, functionalized magnetic nanoparticles have been emerging as viable nanocomposites in various areas, including catalysis. Plenty of fascinating nanocomposites comprising of magnetic species and active centers have been prepared and used as catalysts in various organic reactions. These types of catalysts can be easily recovered from a reaction solution by application of a magnetic field. They also demonstrate reasonable, even promising in some cases, catalytic activities apart from advantages in the catalyst recycle. The benefits have been repeatedly reported in different organic transformations. Therefore, construction and examination of highly efficient magnetic nanocomposites will continue to attract increasing research interests both in academia and in industry. This chapter primarily addresses the commonly used synthetic methodology and recent successful catalytic applications of magnetic nanocomposites.