Leicester Tigers youngster Forsyth will start at centre in one of ten changes to the side that beat host nation Argentina in the first round of group matches.
His Tigers teammates Sam Harrison and Calum Green drop to the bench for the game in Rosario, which kicks off at 6.10pm BST on Wednesday.
Head coach Mark Mapletoft: "We know this is a tough group, but we want to win each game, so we've picked a side to try and do that. At the same time we can't expect 80 minutes from all our players every three days.”
England Under-20s (Stadio El Coloso del Parque, Rosario, Wednesday, June 9 6.10pm BST)
15 Tom Homer (London Irish)
14 Christian Wade (London Wasps)
13 Andrew Forsyth (Leicester Tigers)
12 Tom Casson (Harlequins)
11 Sam Smith (Harlequins)
10 Rory Clegg (Harlequins)
9 Charlie Davies (Stade Francais)
1 Lee Imiolek (Sale Sharks)
2 Jamie George (Saracens)
3 Mako Vunipola (Bristol)
4 George Kruis (Saracens)
5 Charlie Matthews (Harlequins)
6 Jamie Gibson (London Irish)
7 Jacob Rowan (Leeds Carnegie, captain)
8 Alex Gray (Newcastle Falcons)
Replacements
16 Rob Buchanan (Harlequins)
17 Joe Marler (Harlequins)
18 Calum Green (Leicester Tigers)
19 Jackson Wray (Saracens)
20 Sam Harrison (Leicester Tigers)
21 Freddie Burns (Gloucester)
22 Jonny May (Gloucester)
