After conducting escort, ASW, and patrolling duties among the scattered Aleutians, she saw her first action 18 February when, with Indianapolis and Richmond, she bombarded Attu Island, without return fire.

The destroyer shot over 400 rounds of 5-inch into Japanese installations at Holtz Bay and Chichagof Harbor, and on the evening of the same day began an anti-shipping patrol southwest of Attu with Indianapolis and Coghlan.

Through the spring, summer, and fall of 1943 the destroyer made four round-trip transatlantic escort voyages to Casablanca, French Morocco, and return, shepherding troop and cargo ships to the North African theater.

On 2 January 1944, she departed Norfolk, Virginia for the Pacific, reaching Funafuti atoll 20 days later, and escorting troop ships thence to Milne Bay, New Guinea, where she put in 7 February.

On 6 March, the LSTs made landings in Hayne Bay, Los Negros, while Gillespie patrolled from five to fifteen miles off the northeast coast.

She conducted training exercises at Pearl Harbor and closed Ulithi 8 February, and subsequently as part of the Logistic Support Forces she escorted supply ships and units of the 5th Fleet during the seizure of Iwo Jima.

Underway once more 12 October, she sailed via Manila and Pearl Harbor to moor at San Diego 23 November, and steamed thence to close Boston, Massachusetts 11 December.