Wanderer was built in 1897 as the "gentleman's private steam yacht" Kethailes at Leith, Scotland, by Ramage & Ferguson for William Johnston, a wealthy shipowner.

On 28 July 1917, Wanderer departed New York for a brief shakedown before she joined the rest of her division at St. John's, Newfoundland, where she arrived on 9 August 1917.

Wanderer — designed as a pleasure craft, not as sturdy as a warship — had less to fear from German U-boats than from naval mines, weather, and the rocky, foggy shore.

On 12 January 1918, while escorting that convoy from Brest to Quiberon Bay in daylight, Wanderer rescued 10 survivors from the French ship Chateau Faite, which had attempted a night transit.

On the night of 22–23 April 1918, during the layover at Quiberon Bay on the return trip from Bordeaux to Brest, she witnessed the explosion of the ammunition-laden Florence H. .

Though in reasonably close proximity to the ill-fated ship, Wanderer was prevented from approaching the floating conflagration by the large quantity of high explosives she carried to use against U-boats.