Iridium catalyzed alkyne hydroboration with o-carborane cage B-H has been achieved, leading to the formation of a series of 4-B-alkenylated-o-carborane derivatives in high yields with excellent regioselectivity via direct B-H bond activation. In this reaction the carboxy group is used as a traceless directing group, which is removed during a one-pot process. After the confirmation of a key intermediate, a possible mechanism is proposed, involving a tandem sequence of Ir-mediated B-H activation, alkyne insertion, protonation, and decarboxylation.