The ship's main battery consisted of four 12-inch guns mounted in two twin-gun turrets, one forward and one aft. The secondary armament consisted of four 10-inch guns mounted in four single-gun turrets positioned on each side of the superstructure. Katori also carried 12 quick-firing (QF) six-inch guns, mounted in casemates on the sides of the hull and in the superstructure. A number of smaller guns were carried for defence against torpedo boats. These included a dozen QF 12-pounder guns and three 3-pounder Hotchkiss guns. She was also armed with five submerged 18-inch torpedo tubes, two on each broadside and one in the stern.