Following the outbreak of World War I in July 1914, "Yorck" was mobilized for wartime service; she was recommissioned on 12 August. Initially assigned to IV Scouting Group, on 25 August she was transferred to III Scouting Group, under the command of "KAdm" Hubert von Rebeur-Paschwitz. Beginning on 20 September, she was tasked with guarding the German Bight. The ships of III Scouting Group transferred temporarily to the Baltic Sea two days later for a sortie into the central Baltic, as far north as Östergarn, from 22 to 29 September. They then returned to the North Sea and rejoined the High Seas Fleet.