The idea of accepting civilian women’s help in naval wartime efforts was discussed informally in December 1914. Shortages of men for naval service led to the idea being taken up in earnest in autumn 1917. On 26 November, Sir Eric Geddes, the First Lord of the Admiralty, submitted a proposal for a WRNS to King George V, who signified his approval on 28 November 1917. Dame Katherine Fuse was appointed director of this new shore service, whose formation was first mentioned in the Admiralty Office memorandum 245 and in The Times of 29 November 1917.

It was modelled upon the example of the Women's Army Auxiliary Corps, which had been set up in March 1917, in order to release men from shore jobs for service at sea or abroad.

The purpose of the WRNS was to release naval men for the war effort by substituting women for work in establishments administered by the Admiralty. The work was of a clerical, domestic and mechanical nature, for example cooks, telephonists and signals operators, driver-mechanics. Gradually they were introduced into the Royal Navy, Royal Marines, Royal Naval Volunteers, Royal Naval Volunteer Reserve, and Royal Naval Air Division.

The headquarters for the service was set up at 15 Great Stanhope Street, London on 7 January 1918, the first officers were appointed to bases and stations on 18 January and a new entry establishment for ratings was established at Crystal Palace, in South London. Both officers and ratings were classed as either"mobile" (volunteers prepared to serve away from home) or"immobile" ( those who continued to live in their own homes at the ports and find their own board). The officers were graded into various ranks of Director and Principal, while the senior ratings were known as Section Leaders. Divisions were made up of twenty or more sub-divisions which were, in turn, broken down into companies and sections. As well as serving in the United Kingdom, the WRNS was also based abroad: the headquarters of the Mediterranean Division was set up in Malta, with sub-divisions in Gibraltar and Genoa. The WRNS was also based at Royal Naval Air Service stations although these women, numbering about two thousand, transferred to the Women's Royal Air Force on its formation in April 1918. Although there was some pressure to retain the WRNS as a permanent service after the war, an Admiralty Fleet Order of 19 February 1919 announced a process of gradual demobilisation, and by virtue of a final order of 1 October 1919, the WRNS ceased to exist.

During its World War I existence, the WRNS complement reached a peak of 438 officers and 5054 ratings. The present WRNS was re-established on 12 April 1939.