The steam boat Arfon had remained untouched on the bed of the English Channel for almost 100 years until it was discovered in 2014.
The trawler swept mines laid by German U-boats off the Dorset coast until 10 of its 13 crew members died when it struck a mine in April 1917.
The new protection restricts access to the site.
Historic England said the trawler's mine-sweeping gear, deck gun and engine room were still intact on the seabed off St Alban's Head.
But the government heritage agency feared the Arfon, built in Goole, East Yorkshire, in 1908, could be vulnerable to uncontrolled salvage.
The Department for Culture, Media and Sport granted it protection under the Protection of Wrecks Act 1973, which means access to the site is restricted to divers with a licence from Historic England.
Joe Flatman, the body's head of listing programmes, said: "The Arfon shipwreck is a rare survivor of a type of vessel once very common around the coastline of Britain but which has now entirely disappeared, surviving only in documents and as wrecks like this one.
"Trawlers, minesweepers and other coastal patrol vessels played a crucial role in keeping the sea lanes around the British Isles open during both world wars, a part of the war effort that is often overlooked."
The sunken wreck of a fishing trawler that swept for mines during World War One has been given special protection.