Following shakedown off California, "Long Beach" departed San Diego, on 12 January 1944 for Cairns, Australia, arriving there on 17 February 1944. After towing two LCSs from Milne Bay, New Guinea, to Cape Sudest, New Guinea, she departed on 16 March 1944 escorting the dock landing ship to the landings on Manus in the Admiralties. Returning to Cape Sudest on 18 March 1944, "Long Beach" screened ships around New Guinea, and on 19 April 1944 took part in the invasion of Aitape. She sailed for the Schoutens on 6 August 1944 for patrol and shore bombardment duty during cleanup operations against Japanese holdouts in the Biak area, returning to local operations off New Guinea on 31 August 1944.