She was commissioned into the Pola Flotilla of the German Imperial Navy on 26 July 1917 as SM UB-51.

[Note 1] She operated as part of the Pola Flotilla based in Cattaro.

UB-51 was surrendered 16 January 1919 with the remainder of the Pola Flotilla following orders by Admiral Reinhard Scheer to return to port.

Like all Type UB III submarines, UB-51 carried 10 torpedoes and was armed with a 8.8 cm (3.46 in) deck gun.

UB-51 would carry a crew of up to 3 officer and 31 men and had a cruising range of 9,040 nautical miles (16,740 km; 10,400 mi).