Assigned to the 2nd Division, Asiatic Fleet (formalized as the Yangtze Patrol in 1922), Monocacy sailed upriver from Shanghai on 29 June 1914 to cruise between Ichang and Chungking.

A sailor reaching the entertainments of Shanghai with six months' pay in his pockets from the time patrolling upriver claimed to use most of his money for liquor and women, and spend the rest foolishly.

[1] On 16 January 1918, Chinese southern revolutionary troops attacked the little warship 50 miles (80 km) above Chenglin; during which Monocacy prevented the rebels from firing on a Japanese steamer standing down stream.

Based at Shanghai, the gunboat cruised the lower river, making less frequent voyages to her original patrol area between Chungking and Ichang.

Monocacy was at Kiuklang protecting American neutrality during the Japanese invasion of China, when on 29 August 1938 several mines exploded within 80 yards (73 m) of the ship, showering the gunboat with fragments.