They forced the German battlecruiser SMS Goeben to disengage during the Battle of Cape Sarych shortly after Russia declared war on the Ottoman Empire in late 1914.

She covered several bombardments of the Bosphorus fortifications in early 1915, including one where she was attacked by Goeben, but Evstafi, together with the other Russian pre-dreadnoughts, managed to drive her off.

At full load she carried 1,100 long tons (1,118 t) of coal that provided her a range of 2,100 nautical miles (3,900 km; 2,400 mi) at a speed of 10 knots (19 km/h; 12 mph).

They did this successfully on the morning of 17 November and they turned west to hunt for Turkish shipping along the Anatolian coast before setting course for Sevastopol later that afternoon.

They were intercepted by the Turkish battlecruiser Yavuz Sultan Selim and the light cruiser Midilli the following day in what came to be known as the Battle of Cape Sarych.

She scored a hit with her first salvo as a 12-inch shell partially penetrated the armor casemate protecting one of Yavuz's 15-centimetre (5.9 in) secondary guns.

although one shell failed to detonate, before Rear Admiral Wilhelm Souchon decided to turn away and break contact after fourteen minutes of combat.

[9] Several armour plates on Evstafi required replacement after the battle and they were taken from the old pre-dreadnought Dvenadsat Apostolov so that the repairs were completed by 29 November.

[10] On 9 January 1915 Midilli and the Hamidiye encountered the Russian fleet while returning from a mission in the eastern part of the Black Sea.

Midilli hit Evstafi's forward turret with a 10.5-centimetre (4.1 in) shell, temporarily putting it out of action, and the two cruisers escaped using their superior speed.

This manoeuvre bought enough time that Tri Sviatitelia and Pantelimon were able to rejoin the other two ships before they could start shelling the Ottoman forts.

On 1 October the new dreadnought provided cover while Ioann Zlatoust and Pantelimon bombarded Zonguldak and Evstafi shelled the nearby town of Kozlu.

The British wrecked both ships' engines on 22–24 April 1919 when they left the Crimea to prevent the advancing Bolsheviks from using them against the White Russians.