"Nassau" saw service in the North Sea at the beginning of World War I, in II Division of I Battle Squadron of the German High Seas Fleet. In August 1915, she entered the Baltic Sea and participated in the Battle of the Gulf of Riga, where she engaged the Russian battleship . Following her return to the North Sea, "Nassau" and her sister ships took part in the Battle of Jutland on 31 May – 1 June 1916. During the battle, "Nassau" collided with the British destroyer . "Nassau" suffered a total of 11 killed and 16 injured during the engagement.