Carboranes, a three-dimensional class of carbon-boron molecular clusters with remarkable electronic, physical, chemical characteristics, have proved as useful building blocks in boron neutron capture therapy agents, supramolecular design, optoelectronics, nanomaterials and organometallic/coordination chemistry. Thus, various organic modifications of the BÀ H and CÀ H functionalities in carboranes have been developed. These methods with great success utilize directing groups, such as carboxylic acids, to achieve a selective BÀ H functionalization of carboranes. The carboxyl group can be easily introduced to carboranes and then be removed after reactions. On the other hand, assisted by the carboxyl group a highly regioselective electrophilic attack at the electron-rich positions B(4) and B(5) of the cage generates five-membered metallacyclic intermediates, which then undergo further transformation. In this review, we show that transition metal-catalyzed decarboxylation cross coupling reactions offer an opportunity for the selective and direct BÀ H activation of carboranes. 1. Introduction 2. Formation of BÀ C(sp 2 ) Bonds 3. Formation of BÀ C(sp) Bonds 4. Formation of BÀ C(sp 3 ) Bonds 5. Formation of BÀ N Bonds 6. Formation of BÀ O Bonds 7. Formation of BÀ X Bonds 8. Formation of BÀ N Bonds and BÀ C(sp 2 ) Bonds 9. Formation of CÀ N Bonds 10. Conclusions and Outlooks