Completing conversion at New York City on 26 May 1942, Libra loaded combat equipment at Hampton Roads and sailed on 10 June for Wellington, New Zealand, arriving 11 July.

Libra arrived off Tulagi on 7 August, and began an unloading interrupted six times in the next three days, as enemy air attack caused her to go to general quarters and stand off to maneuver in open waters.

In the early morning 9 August she heard heavy gunfire to the northwest, where Allied warships engaged the Japanese in the Battle of Savo Island, fighting to protect the transports and their vital cargo.

She sailed for Espiritu Santo on 13 November as the Battle of Guadalcanal, just south of Savo Island, raged to a victory which gave the Allies sea control off the southern Solomons.

Returning to Espiritu Santo on 15 November, Libra prepared for two additional voyages to Guadalcanal during the next month, bringing cargo essential to the epic struggles of the marines to wrest the island from the Japanese.

Aside from a repair period in New Zealand in August, Libra gave the next four months to building up the base on Guadalcanal with cargo from New Caledonia, then was part of the assault force for Bougainville, arriving Empress Augusta Bay on 1 November.

Promptly unloading, she sailed the same day for Guadalcanal for additional cargo, with which she arrived Bougainville on 8 November, immediately to splash one of 25 dive bombers attacking her transport group.

With the increased demand on cargo facilities brought on by the Korean War, Libra recommissioned 28 August 1950 to join the Amphibious Force, Atlantic Fleet, supporting its training operations along the east coast and in the Caribbean.