Icosahedral carboranes constitute a class of structurally unique molecules with exceptionally thermal and chemical stabilities, which limits the derivatization of these clusters. In view of the spectacular role of transition metals in synthetic chemistry, novel o-carborane functionalization methods for both cage carbon and boron vertices have been developed by using transition metal-promoted reactions. These methods offer a series of exceptionally efficient synthetic routes to a wide range of functionalized carboranes from readily available starting materials. An overview of recent advances in this field is presented in this digest. (C) 2015 Elsevier Ltd.