Positional changes see Bath's Tom Heathcote move to fly half from inside centre and Harlequins' Charlie Walker makes the switch from full back to wing.
England lead the way in Pool B after their nine-try win, but face a confident Irish side looking to make it two wins from two after beating hosts South Africa 23-19.
Assistant coach Nick Walshe says that England have recovered well and are ready for the Irish challenge:
"The Italy game was tough but we've had a few days to get ready and the boys are looking fresh," he said.
"Ireland had a fantastic result against South Africa so full credit to them for that, but we weren't surprised by it because we know what a good side they are and they can't be underestimated."
On Mills captaining the side, Walshe added:
"Ryan brings with him a lot of experience, and a lot of talent. He played in last year's competition and he's a player the boys will follow and respond to on the field."
England Under 20 starting XV against Ireland
15 Tommy Bell (London Wasps)
14 Marland Yarde (London Irish)
13 Will Addison (Sale Sharks)
12 Ryan Mills (Gloucester Rugby) (C)
11 Charlie Walker (Harlequins)
10 Tom Heathcote (Bath Rugby)
9 Ben Spencer (Saracens)
1 Alec Hepburn (London Wasps)
2 Koree Britton (Gloucester Rugby)
3 Kyle Sinckler (Harlequins)
4 Dominic Barrow (Leeds Carnegie)
5 George Merrick (Harlequins)
6 David Sisi (London Irish)
7 Ben Nutley (Northampton Saints)
8 Jack Clifford (Harlequins)
16 Max Crumpton (Saracens)
17 Luke Cowan-Dickie (Exeter Chiefs)
18 Ross Harrison (Sale Sharks)
19 Sam Twomey (Harlequins)
20 Chris Walker (Leeds Carnegie)
21 Dan Robson (Gloucester Rugby)
22 Sam Hill (Exeter Chiefs)
23 Ben Ransom (Saracens)
Content courtesy of RFU