In 1938, the Australian Commonwealth Naval Board (ACNB) identified the need for a general purpose 'local defence vessel' capable of both anti-submarine and mine-warfare duties, while easy to construct and operate.

[6] The need for locally built 'all-rounder' vessels at the start of World War II saw the "Australian Minesweepers" (designated as such to hide their anti-submarine capability, but popularly referred to as "corvettes") approved in September 1939, with 60 constructed during the course of the war: 36 (including Deloraine) ordered by the RAN, 20 ordered by the British Admiralty but manned and commissioned as RAN vessels, and 4 for the Royal Indian Navy.

[1] She was launched on 26 July 1941 by Dame Mary Hughes, wife of the Minister for the Navy, and commissioned into the RAN on 22 November 1941.

[1] After commissioning, Deloraine sailed to Darwin, where she was based for the first part of her career as a convoy escort and anti-submarine patrol vessel.

[1] They were successful, and the four ships were jointly credited with the kill of I-124—the first enemy submarine to be sunk in Australian waters, going down with 80 lives.

[11][12] After refitting, Deloraine was used to transport an occupation force from Morotai to Menado, then returned to Sydney and commenced clearing minefields off the New South Wales coast.