Copper-catalyzed electrochemical selective cage B-H oxygenation of o-carboranes has been achieved for the first time. Under a constant electric current (4.0 mA) at room temperature, copper-catalyzed cross-coupling of carboranyl amides with lithium phenolates results in the formation of B(4,5)-diphenolated o-carboranes via direct B-H activation, whereas the use of lithium tert-butoxide affords B(4)-monooxygenated products. This reaction does not require any additional chemical oxidants and generates H2 and a lithium salt as byproducts. Control experiments indicated that a high-valent Cu(III) species is likely involved in the reaction process.