USS Pensacola made a shakedown cruise to Peru and Chile. After this shakedown she began regular operations in the western Atlantic, Caribbean and Pacific. Pensacola shifted home port from Norfolk, Virginia, to San Diego, California, in January 1935 and thereafter mainly served in the Pacific.

When the Pacific War began on 7 December 1941 with Japan's attack on Pearl Harbor, Pensacola was at sea escorting a convoy that was subsequently diverted to Australia. Following patrols in the vicinity of Samoa, the cruiser screened the carriers Lexington and Yorktown during their operations in the southern Pacific from February into April 1942. In the early June Battle of Midway Pensacola escorted both USS Enterprise and USS Yorktown. From August to December 1942, she operated in support of the Guadalcanal campaign, mainly serving with aircraft carriers, and was present during the Battle of the Santa Cruz Islands in late October and the Naval Battle of Guadalcanal in mid-November. At the end of November, Pensacola was badly damaged by a torpedo in the Battle of Tassafaronga, with the loss of 125 and 72 were wounded.

Pensacola was under repair until well into 1943, but returned to service in time to participate in the Tarawa invasion in November. In 1944 she took part in the conquest of the Marshall Islands and operated with carrier striking forces during raids in the central Pacific. From May into August, she patrolled in the north Pacific and bombarded Japanese positions in the Kurile Islands. Moving south, Pensacola shelled Wake Island in September and Marcus in early October, then joined the Third Fleet's carrier forces to participate in attacks on Formosa and in the Battle of Leyte Gulf.

Target ship at Bikini in July 1946/.
Decommissioned 26 August 1946.
Stricken and sunk 10 November 1948.