"Princess Royal" served in the Battle of Heligoland Bight a month after the war began and then was sent to the Caribbean to prevent the German East Asia Squadron from using the Panama Canal. After the East Asia Squadron was sunk at the Battle of the Falkland Islands by the two "Invincible"-class battlecruisers, "Princess Royal" rejoined the 1st Battlecruiser Squadron. During the Battle of Dogger Bank she scored only a few hits, although one directly crippled the German armoured cruiser , which allowed the enemy vessel to be caught and sunk by the concentrated fire of the British battlecruisers. Shortly afterwards "Princess Royal" became the flagship of the 1st Battlecruiser Squadron, under the command of Rear Admiral Osmond Brock. She was moderately damaged during the Battle of Jutland and required a month and a half of repairs. Both ships spent the rest of the war on uneventful patrols in the North Sea, although they did provide distant cover during the Second Battle of Heligoland Bight in 1917. In 1920 they were both put into reserve and were sold for scrap a few years later under the terms of the Washington Naval Treaty.