Palladium-catalyzed regioselective di- or mono-arylation of o-carboranes was achieved using weakly coordinating amides at room temperature. Therefore, a series of B(3,4)-diarylated and B(3)-monoarylated o-carboranes anchored with valuable functional groups were accessed for the first time. This strategy provided an efficient approach for the selective activation of B(3,4)-H bonds for regioselective functionalizations of o-carboranes. This journal is © The Royal Society of Chemistry.