The third USS Adirondack (AGC-15) was laid down on 18 November 1944 under a Maritime Commission contract by the North Carolina Shipbuilding Company in Wilmington, North Carolina; launched on 13 January 1945, sponsored by Mrs. E. L. White; transferred to the Navy on 4 February 1945; towed to the Philadelphia Naval Shipyard for conversion; and commissioned on 2 September 1945, the day Japan surrendered on board the battleship Missouri (BB-63) in Tokyo Bay.

Following a shakedown and training cruise to Guantanamo Bay, Adirondack headed back to Norfolk, Virginia, and on 28 October, became flagship for Commander, Amphibious Force, Atlantic Fleet.

In April COMPHIBGRU FOUR—still embarked in Adirondack – was designated Commander of the umpire group for LANTAGLEX-54, a full-scale amphibious assault on Onslow Beach, North Carolina.

Another exercise, "Packard V," was held in May and consisted of a naval gunfire demonstration in the Chesapeake Bay and a full-scale D-day assault on Onslow Beach, directed from Adirondack by COMPHIBGRU FOUR.

On 20 July, the ship departed Norfolk for Operation Keystone, a combined land, sea, and air maneuver in the Mediterranean involving forces of the countries of the North Atlantic Treaty Organization.

After a successful drill, Adirondack sailed on 3 November for Bogue Inlet, North Carolina, for a full-scale assault climaxing the amphibious phases of the Atlantic Fleet training cycle for 1954.

During 1955, Adirondack served as umpire for "ANGEX II," a naval gunfire exercise held in February off Vieques and Culebra, Puerto Rico.