The ship's main armament consisted of sixteen quick-firing (QF) QF 4.5-inch Mk I – V naval gun dual-purpose guns in eight twin-gun turrets, four in sponsons on each side of the hull. Unlike the "Illustrious"-class ships, the roofs of the gun turrets were flat and flush with the flight deck. The gun had a maximum range of . Her light anti-aircraft defences included five octuple mounts for QF 2-pounder ("pom-pom") anti-aircraft (AA) guns, two on the flight deck forward of the island, one on the aft part of the island and two in sponsons on the port side of the hull. A single quadruple 2-pounder mount was also fitted on the port side of the hull. The 2-pounder gun had a maximum range of . The ship was also fitted with 61 Oerlikon 20 mm autocannon in 19 single and 21 twin-gun mounts. These guns had a maximum range of , but some were replaced by 40 mm Bofors AA guns when the ships were transferred to the Pacific Theater as the 20 mm shell was unlikely to destroy a kamikaze before it hit the ship. The Bofors gun had a maximum range of . Two additional quadruple "pom-pom" mounts were added to "Implacable" before she joined the British Pacific Fleet in 1945. By the end of the war, she had 4 single Bofors guns, plus 17 twin and 17 single Oerlikon mounts. By April 1946 these had been reduced to 12 Bofors guns, 8 twin and 14 single Oerlikon guns.