During the Battle of Jutland on 31 May 1916, she was the flagship of Rear-Admiral Sir Robert Arbuthnot, leading the First Cruiser Squadron. The squadron formed the starboard flank of the cruiser screen, ahead of the main body of the Grand Fleet. "Defence" was just to the right of the centre of the line. At 5:47 p.m., "Defence" and , the leading two ships of the squadron, spotted the German II Scouting Group and opened fire. Their shells fell short and the two ships turned to port in pursuit, cutting in front of the battlecruiser , which was forced to turn away to avoid a collision. Shortly afterwards, they spotted the disabled German light cruiser and closed to engage. When the two ships reached a range of from "Wiesbaden" they were spotted in turn at 6:05 by the German battlecruiser and four battleships which were less than away. The fire from the German ships was heavy and "Defence" was hit by two salvoes from the German ships that caused the aft 9.2-inch magazine to explode. The resulting fire spread via the ammunition passages to the adjacent 7.5-inch magazines which detonated in turn. The ship exploded at 6:20 with the loss of all men on board; between 893 and 903 men were killed.