In the years that preceded World War I, Fanning took part in the training schedule of the Atlantic Fleet, sailing to the Caribbean for winter maneuvers, and exercising off the coast of New England in the summers.

When two German auxiliary cruisers visited Norfolk in September 1916, Fanning acted as part of their escort while they sailed in United States territorial waters.

During the latter half of October 1916, Fanning and the fuel ship Jason conducted experiments to develop methods of oiling at sea, a technique which has since given the United States Navy unbounded mobility and sea-keeping qualities.

At 1615 on 17 November 1917, Coxswain Daniel David Loomis sighted the periscope of U-58, and the Officer of the Deck Lieutenant Walter Owen Henry ordered the destroyer to attack.

Fanning's first depth charge pattern scored, and as destroyer Nicholson joined the action, the submarine broke surface, her crew pouring out on deck, hands raised in surrender.

After a quick voyage to Plymouth, England, Fanning departed Brest for the States, by way of Lisbon, Portugal, and Ponta Delgada, Azores, in company with several other destroyers, and escorting a large group of submarine chasers.