At the outbreak of World War I, the yacht was leased by the United States Navy, and was used as a section patrol craft in the North Atlantic Ocean.

At war’s end, she was converted to her original configuration and returned to her owner, the railroad executive, financier, and philanthropist Frederick W. Vanderbilt (1856-1938) of New York City.

Vedette and five other patrol vessels - all former yachts - got underway from Tompkinsville on Staten Island, New York, bound for Bermuda on 9 June 1917 on the first leg of their voyage to France.

Vedette spotted "considerable floating wreckage and a cork life belt" upon which no name was visible on the evening of 2 July 1917.

The squadron sighted the French coast at 0440 on 4 July 1917, but before they could make it into port, Christabel broke down and Vedette stood by until she could get underway again.

The two ships initially headed for the middle of the patrol line 10 nautical miles (18.5 kilometers) off the coast, extending from the northward and westward of Ushant to the southward of Belle Île.

Vedette returned to Brest on 19 July 1917, without having met the enemy, but she did encounter more wreckage, including life rings from an unidentified ship.

While en route in, Harvard broke down, and Vedette stood by until her longstanding partner was ready to proceed.

Still en route to Brest during the pre-dawn hours of 6 August 1917, Vedette sighted a "suspicious vessel" at 0320 and opened fire with her number two 3-inch (76.2-mm) gun.

After the work was completed during the forenoon watch (0800-1200) on 7 August 1917, the ship was towed back to her former berth, where she provisioned and made ready to return to the Ushant-Brest patrol line.

A British merchantman, last in line of the convoy, had struck a naval mine; nearby, a French vessel rescued 14 men before the rapidly sinking ship disappeared.

Unable to make contact with the enemy, the yacht picked up 27 men from a lifeboat, including the master of Pontoporos, a Captain Panas, at 0715.

Vedette continued the same routine of operations — interspersed with periods of upkeep, maintenance, and provisioning — through the remainder of the summer and autumn of 1917 and into 1918.

By January 1918, the ship's armament reflected the multi-national character of the escort work performed out of Brest, for not only did she carry her original allotment of 10 American Sperry Mk.

At 0924, Vedette's watch felt a slight jar; within a minute, they saw that the merchant ship SS Hundvaago had taken a torpedo and was sinking rapidly.

At 0927, Signalman 3rd Class Nye, Chief Quartermaster Teiper, and the officer of the deck saw a submarine off the starboard quarter of the convoy.

At one minute past noon, a French seaplane, attracted to the scene of the torpedoing, dropped a smoke bomb, indicating the presence of what looked like a submarine.

She soon picked up a small oil wake about 200 yards (183 m) east of the smoke bomb and dropped a barrage of eight depth charges at 1215.

Less than a month after the Armistice with Germany stilled the guns of World War I on 11 November 1918, she departed Brest for the last time when she weighed anchor on 6 December 1918 for the long voyage home.