Taylor, 36, turned in another classic performance, winning every round against her rangy opponent to extend her unbeaten record to 22 fights.
The Bray Bomber convincingly won her 16th world-title fight six months after her historic split-decision win over Amanda Serrano at New York's Madison Square Garden.
Argentina's Carbajal, 32, from Buenos Aires, proved a worthy challenger, but lost for the first time in 20 fights after coming second best in all departments.
Taylor, who turned professional in 2016, showed superior hand speed, footwork and greater accuracy, and pressed home her advantage in the second half of the bout.
Carbajal felt the full weight of Taylor's punches in round five as the Irishwoman's timing improved and a left-right combination had the South American grimacing.
Taylor displayed her full range of skills in the seventh round and underlined her superiority with three more unanswered punches. In the eighth, Carbajal was knocked off balance by two quick left hooks.
Carbajal came out swinging in the penultimate ninth round and was cut on the right side of her face following an accidental clash of heads.
Taylor had the fight won heading into the final round, but in typical fashion chased a grandstand finish as two looping right hands jolted her opponent, who was ultimately outclassed.