Carborane cage chirality is an outstanding issue of great interest as the icosahedral carboranes have wide applications in medicinal and materials chemistry. The synthesis of optically active carborane derivatives, whose chirality is associated with the substitution patterns on the polyhedron, will open new avenues to carborane chemistry. We report herein an efficient method to achieve chiral-at-cage arylation of o-carboranes with high regio- and enantioselectivities by a strategy of palladium-catalyzed asymmetric intramolecular B-H arylation and cyclization. This represents the first example of the enantioselective reaction on carboranes, providing an efficient way for the construction of chiral-at-cage compounds with new skeletons.