The boats of the S138 class varied in dimensions, and they gradually increased in size as more vessels were built.

When serving as half-flotilla flagships, the boats would have a flotilla leader's staff of four officers and nine enlisted men in addition to the standard crew.

The rest of the members of the class received direct steam turbines of various manufacturers, including AEG, Schichau-Werke, Zoelly, Germaniawerft, and Parsons.

[2] The reciprocating engine-powered boats were rated at 30 knots (56 km/h; 35 mph) from 10,800 to 10,800 indicated horsepower (10,900 to 11,000 PS).

As a result, cruising radius varied significantly, from 920 to 3,500 nautical miles (1,700 to 6,480 km; 1,060 to 4,030 mi) at 17 knots (31 km/h; 20 mph).

The remainder of the class carried two 8.8 cm SK L/30 guns, also with two hundred shells.

V187 was sunk during the Battle of Heligoland Bight on 26 August 1914, one of the first major naval actions of the war.

[7] V150 accidentally collided with her sister ship V157 while the pair were cruising in the Jade Bight shortly after midnight on 18 May 1915.

[7] On 17 December 1915, V191 and the light cruiser Bremen ran into a Russian minefield off Windau; both vessels struck mines and sank, with heavy loss of life.

[12] The Muavenet-i Milliye in Ottoman service successfully torpedoed and sank the British pre-dreadnought battleship HMS Goliath on 13 May 1915 during the Dardanelles campaign, killing 570 of her crew.

All of the boats were scrapped in the early 1920s, with the exception of T189, which ran aground off the English coast in December 1920.

Among those stricken by the postwar Reichsmarine to comply with the Versailles Treaty were T142, T147, T167, T168, T170; these boats were also scrapped in the early 1920s.

In 1932, T185 was renamed Blitz and converted into a radio control ship to replace her sistership in that role.

[6] By the outbreak of World War II in September 1939, only a handful of the class remained in service.

T157 was mined and sunk in Neufahrwasser on 22 October 1943 and T156—which had been renamed Bremse in 1944—and T155 were scuttled in the final days of the war.

V185 and V196 were taken as Soviet war prizes and were renamed Vystrel and Pronzitelnyy, respectively; their ultimate fate is unknown.