A hamstring injury sustained in training by winger George Gasson has ruled him out of the tournament. He is replaced by Ebbw Vale teenager Jared Rosser.
The talented Rosser made his debut for the Steelmen as a then 17-year-old this season. He scored the decisive try in their Principality Premiership Play-off semi-final victory against Llandovery and also went on to be a member of the victorious Ebbw Vale side which swept aside Pontypridd in the Premiership final at Sardis Road.
Wales U20 team manager Mark Taylor, said: "It's obviously disappointing to lose a player of George's ability so close to the tournament but Jared is now given an opportunity and his selection is reward after a fine season with Ebbw Vale."
Wales take on Ireland, Georgia and New Zealand in Pool A of the global tournament, with Six Nations opponents Ireland first up at the Manchester City Academy Stadium (5.30).
An Ebbw Vale spokesman added: "All at the club are delighted for Jared, it is a major achievement to make the U20's World Cup for someone who has only recently turned 18.
"It is reward for the hard work he has put in and the coaches at Ebbw Vale have been delighted with his progress on the field and his attitude and behaviour off it. This is a credit to himself, his family and the Dragons Academy."
Jared Rosser
DOB: 31st Dec, 1997
Birthplace: Monmouth
Height: 1.83m (6ft)
Weight: 98kg (15st 6lb)
Position: Winger
Club: Ebbw Vale
