The 18-year-old England youth international had attracted the attention of several clubs once it became apparent he would not extend his stay with the Hammers, but it is Leeds who have won his signature.
Perkins made appearances in the Premier League and Europa League for the London club last season, coming off the bench against the Whites during Leeds’ 3-2 victory at the London Stadium, as well as featuring against GNK Dinamo Zagreb in Europe.
Son of former Ireland Under-21 international Declan Perkins, Sonny has represented England at several age groups and is currently an Under-18 international.
“Sonny becomes the club’s seventh summer signing, after the arrivals of Brenden Aaronson, Rasmus Kristensen, Marc Roca, Darko Gyabi, Tyler Adams and Luis Sinisterra,” a statement from Leeds United read.
“He will initially link up with the Under-21s side for the forthcoming season.”
Check out the latest Premier League transfer speculation below...
1. O’Brien deal back on
Lewis O’Brien and Harry Toffolo have agreed to sign for Nottingham Forest, despite reports on Tuesday suggesting that the double deal had collapsed. (Football Insider) | Getty Images
2. Wolves eye Benteke
Christian Benteke is a target for Wolves. The Crystal Palace striker has one year left of his current deal. (The Sun) | Getty Images
3. Gunners offered Akanji
Arsenal have been offered the opportunity to sign Borussia Dortmund central defender Manuel Akanji this summer. The German club are looking for a fee in the region of £21m. (Gazzetta Dello Sport) | Getty Images
4. Hammers in Lingard talks
West Ham are in negotiations with Jesse Lingard’s representatives with a growing feeling the player will opt for a return to the club this summer. (Sky Sports) | Manchester United via Getty Imag
5. Davis set for exit
Leeds United are ‘likely to sanction’ the exit of Leif Davis for a seven-figure fee in the coming weeks. (East Anglian Daily Times) | Getty Images
6. City eye Cucurella
Manchester City are preparing to lodge an official bid for Brighton left-back Marc Cucurella ‘as soon as possible’. (Fabrizio Romano) | Getty Images