She was commissioned into the German Imperial Navy on 1 August 1917 as SM UB-66.

[Note 1] UB-66 was sunk by HMS Campanula at 38°30′N 24°25′E / 38.500°N 24.417°E / 38.500; 24.417 on 18 January 1918, 30 crew members died in the event.

UB-66 was commissioned later that same year under the command of Kptlt.

Like all Type UB III submarines, UB-66 carried 10 torpedoes and was armed with a 8.8 cm (3.46 in) deck gun.

UB-66 would carry a crew of up to 3 officer and 31 men and had a cruising range of 9,090 nautical miles (16,830 km; 10,460 mi).