The change means there are now three changes in the starting line-up from the side that played France in the final Under 20 Six Nations game this year. In addition to Hamilton replacing Young, Dragons and Newport back Lewis Robling will make his Wales Under 20 debut, partnering Owen Williams in the centre, while Eli Walker makes his first start on the left wing since he was injured in the the win over Scotland in the second game of the Under 20 Six Nations.
Wales head coach Richard Webster said: "We are pleased with the strength of the side we've been able to select for this game. It's important we get off to a good start in our opening game, or we will make things very difficult for ourselves further on in the competition.
"The boys have settled in well since arriving on Monday, enjoying a couple of good training sessions, despite the torrential rain all week."
Wales U20 team v Argentina Friday 10 June, 18.10, Stadio Plebiscito, Padua (17.10 kick-off UK time, live on S4C)
Steve Shingler (London Irish); Liam Williams (Llanelli), Owen Williams (Blues / Cardiff), Lewis Robling (Dragons / Newport), Eli Walker (Ospreys / Swansea); Matthew Morgan (Ospreys / Swansea), Jonathan Evans (Dragons / Newport); Rhodri Jones (Scarlets / Llanelli), Kirby Myhill (Scarlets / Llanelli), Will Taylor (Ospreys / Swansea), Macauley Cook (capt, Blues / Cardiff), Cory Hill (Blues / Pontypridd), Edward Siggery (Pontypridd), Thomas Young (Blues / Cardiff), Ben Thomas (Ospreys / Bridgend).
Replacements: Lewis Smout (Blues / Pontypridd), WillGriff John (Blues/ Pontypridd), Lloyd Peers (Ospreys / Bridgend), Owen Sheppeard (Blues / Pontypridd), Lewis Jones (Blues / Pontypridd), Rheon James (Scarlets/ Carmarthen Quins), Iolo Evans (Scarlets / Llanelli)