Catclaw reported at New London, Connecticut, 10 April 1944 to lay experimental underwater detection and sonar gear until 10 June.

On 20 August she arrived at Cherbourg, where she based until 14 September while laying moorings at Morlaix Roads for cargo ships bypassing the harbor at Brest.

Through November, she played an essential part in the huge task of clearing the harbor of Le Havre, and after a month of operations at Plymouth, England, sailed for Charleston, South Carolina, 9 January 1945, aiding in the escort of a group of disabled ships including LCT-421 which she took in tow.

After overhaul, Catclaw sailed from Charleston 15 February 1945 for San Diego, California, to load nets for Pearl Harbor.

From 10 September to 14 October, she laid harbor buoys and issued dry stores at Sasebo, then returned to Okinawa to load acoustic minesweeping equipment for use in Japanese waters.