Hancock sailed from San Francisco for the East Coast 14 December 1902 via Valparaiso, Chile; Montevideo, Uruguay; and Bahia, Brazil.

[3][1] She landed the Marines at Vera Cruz, Mexico, to assist in the occupation of that city resulting from the arrest of the crew of a whaleboat of Dolphin (PG-24) by soldiers of General Huerta, aspirant to the Mexican presidency.

As a result, as the diplomatic crisis with Mexico eased, Hancock embarked a battalion of Marines from Vera Cruz and transported them to Guantanamo, Cuba.

She continued to transport Marines, stores, provisions, mail, and other cargo to forces ashore in Mexico, Haiti, and Santo Domingo.

On 6 April 1917 the United States declared war on Germany six days later Hancock took possession of German steamers Wasgenwald and Calabria interned there.

She embarked 29 German prisoners of war 23 May 1917, and stood out of San Juan harbor that afternoon to tow Odenwald to the Philadelphia Navy Yard where she arrived 1 June 1917.

Returning to Philadelphia 22 July 1917, her principal service until September 1919 was transportation of Marine passengers and military stores to ports in the West Indies and the Gulf of Mexico.

Hancock recommissioned 15 March 1920 and departed Philadelphia 2 April 1920 for Rosyth, Scotland, to man and fit out former German warships SMS Ostfriesland and Frankfurt which had been allocated to the United States as spoils of war.