Dewey spent 1944 supporting raids in the Marshalls, Carolines, and Marianas, including screening carriers during the Battle of the Philippine Sea.

After being damaged by Typhoon Cobra during the Recapture of the Philippines, Dewey supported the invasion of Iwo Jima and spent the remainder of the war screening replenishment oilers.

Dewey arrived at Pearl Harbor 12 October 1939 and participated in tactical exercises, battle practice, fleet problems, and maneuvers until 1941.

On 5 May word came that the Japanese were advancing on Port Moresby, and Dewey's group joined the Yorktown in the battle of the Coral Sea.

She went to the rescue of two ships, aiding the Jarvis to regain power, and towing the George F. Elliott until her damage made it necessary to abandon her.

She escorted the Saratoga, damaged by submarine torpedo 31 August, to Pearl Harbor, arriving 23 September, and 6 days later sailed for overhaul at San Francisco.

When the Worden ran aground at Amchitka, Dewey attempted to tow her off the rocks, then aided in rescuing her survivors when stormy weather forced her abandonment.

During the Marianas landings, Dewey screened the carriers during the resulting Battle of the Philippine Sea on 19 and 20 June, and rescued several pilots and crew members who were forced to ditch.

She screened this group in its refueling operations for the Philippines invasion until the typhoon of 18 December, which heavily damaged the units of the 3rd Fleet.

Dewey had lost all power by noon, and was rolling more than 75 degrees; her number one stack was torn and thrown against the boat deck.

After escorting a convoy to Leyte from 4 to 6 March 1945, Dewey rejoined the logistics group for the Okinawa operation, screening the oilers as they refueled the carriers in preinvasion air strikes and the raids in the Far East, which continued until the end of the war.