Vieira is part of an 18-man squad who will travel to France next week to take part in a competition which runs from May 23 to June 10.
The 18-year-old turned professional at Elland Road little over a year ago but established himself as a first-team regular under Garry Monk this season, playing 38 times as Leeds finished seventh in the Championship.
Former Derby County manager Steve McClaren singled the teenager out for praise after Derby were beaten 1-0 at Elland Road in January and Vieira’s performances have attracted the attention of England’s youth-team coaches.
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Vieira, who came to Leeds via the i2i Academy, was born in the African state of Guinea-Bissau and spent part of his childhood in Portugal but he has lived in England for several years.
Speaking recently, Vieira told The Sun: “My choice will always be Portugal. If they don’t come, I’m eligible to play for England.”
He was handed his first professional deal by United last May, making his debut at Preston North End two days later, but Leeds moved to offer him an improved three-year contract in September following his rapid progression under Monk.
England’s Under-20s will attempt to progress to the semi-finals of the Toulon Tournament during Group A games against Angola on May 29, Cuba on June 1 and Japan on June 4.
Brazil, France and the Czech Republic are among the other nations involved.
Full England Under-20 squad - Goalkeepers: Ellery Balcombe (Brentford), Ryan Schofield (Huddersfield Town);
Defenders: Ezri Konsa (Charlton Athletic), Cameron Borthwick Jackson (Manchester United), Japhet Tanganga (Tottenham Hotspur), Reece James (Chelsea), Joshua Tymon (Hull City)
Midfielders: Harvey Barnes (Leicester City), David Brooks (Sheffield United), Demetri Mitchell (Manchester United), Sadou Diallo (Manchester City), Tariq Uwakwe (Chelsea), Ronaldo Vieira (Leeds United), Andre Dozzell (Ipswich Town);
Forwards: Elliot Embleton (Sunderland), Daniel Kemp (West Ham United), Luke Bolton (Manchester City), George Hirst (Sheffield Wednesday), Martell Taylor-Crossdale (Chelsea), Ike Ugbo (Chelsea)