"York" lacked a full waterline armor belt. The sides of her boiler and engine rooms were protected by of armour and sides of the magazines were protected by of armour. The transverse bulkheads at the end of her machinery rooms were thick. The top and ends of the magazines were three inches thick. The lower deck over the machinery spaces and steering gear had a thickness of . Space and weight was reserved for one catapult and its seaplane, but they were not fitted until after she was completed. A second catapult, intended to be mounted on 'B' turret, was deleted from the design during construction.