Ostrich was laid down 10 November 1943 as YMS-430 by the Tacoma Boat Building Co. of Tacoma, Washington; launched 23 March 1944; and commissioned 10 October, Lt. R. G. Bates in command. After shakedown, she sailed for Pearl Harbor 19 December as part of a screen for a small convoy. She arrived 28 December and sailed 4 January 1945, escorting a convoy to Eniwetok. She then sailed to Ulithi arriving 5 February. She remained in the area until departing 14 June for Okinawa to engage in Minesweeping operations.