After shakedown training in Chesapeake Bay, San Diego sailed via the Panama Canal to the west coast, arriving at her namesake city on 16 May 1942. Escorting Saratoga (CV-3) at best speed, San Diego barely missed the Battle of Midway. On 15 June, she began escort duty for Hornet (CV-8) in operations in the South Pacific. Early in August, she supported the first American offensive of the war, the invasion of the Solomons at Guadalcanal. With powerful air and naval forces, the Japanese fiercely contested the American thrust and inflicted heavy damage; San Diego witnessed the sinking of Wasp (CV-7) on 15 September and of Hornet on 26 October.
San Diego gave antiaircraft protection for Enterprise (CV-6) as part of the decisive three-day Naval Battle of Guadalcanal, 12 to 15 November 1942. After several months of service in the dangerous waters surrounding the Solomon Islands, San Diego sailed via Espiritu Santo, New Hebrides, to Auckland New Zealand, for replenishment.
She was decommissioned and placed in the Pacific Reserve Fleet on 4 November 1946, berthed at Bremerton, Washington. She was redesignated CLAA-53 on 18 March 1949. Ten years later, she was struck from the Naval Vessel Register, on 1 March 1959.
San Diego received 15 battle stars for service in World War II.
- New arrangement of bridge structure
- Updated radar for USS San Diego
- Improved 120mm cannons
- Updated 20mm single mount guns
- Updated 40mm Bofors quad mount cannons
- New 1.1″ machine cannons by photo-etched part
- Photo-etched racks for depth charges
- Deck railings rendered by photo-etched parts
- New life rafts (2 types)
- New Cartograf decals