Both sides have something to prove after finishing bottom of their respective pools. Ireland suffered defeats to France, England and tournament hosts Argentina, while Samoa lost out to Wales, defending champions New Zealand and Fiji.
Irish coach Allen Clarke have made nine changes in personnel, some enforced, for this must-win clash.
In the backs, a tournament-ending injury to Darren Hudson sees Andrew Boyle, a recent call-up to the squad, make his first start of the tournament on the right wing.
Hudson's place in the extended squad has been taken by Mike Kelliher (Richmond/Munster).
There is a new centre pairing of Leinster duo Brendan Macken and David McSharry, and Ulster's Michael Heaney comes in for his first start at scrum half, partnering Noel Reid in a new half-back combination.
Hooker and team captain Niall Annett will be flanked by two first-time starters in the front row, Bryan Cagney and recent arrival Martin Moore. Fellow prop Jack O'Connell has returned to Ireland to have treatment on an injury.
Moore turned 19 in March and was part of the Ireland Under-19 side that scored notable wins over Australia and France earlier in the season.
David O'Callaghan and Dominic Ryan have dropped down to the replacements bench, allowing Munster pair Brian Hayes and Brian O'Hara a chance to impress in the second row and back row respectively.
Macken, Reid, Heaney, Hayes and O'Hara all saw action as replacements in Ireland's last game in Pool B, a 24-21 loss to Argentina in Rosario.
Ireland and Samoa met in a 7th-8th place play-off at last year's IRB Junior World Championship in Japan, with the young Samoans claiming a tight 9-3 win.
Current squad members O'Callaghan, Ryan, Hayes, O'Connell and Rhys Ruddock, who is Down Under with the senior squad, played against the Samoans twelve months ago.
IRELAND UNDER-20 Team & Replacements (v Samoa U-20s, IRB Junior World Championship, Club Atletico Estudiantes, Parana, Thursday, June 17, kick-off 1pm local time/5pm Irish time):
15 - Andrew Conway (Blackrock College/Leinster)
14 - Andrew Boyle (UCD/Leinster)
13 - Brendan Macken (Blackrock College/Leinster)
16 - David Doyle (UCD/Leinster)
17 - Denis Buckley (Corinthians/Connacht)
18 - David O'Callaghan (UCC/Munster)
19 - Dominic Ryan (Lansdowne/Leinster)
20 - John Cooney (UCD/Leinster)
21 - James McKinney (Queen's University/Ulster)
22 - Eoin Griffin (Corinthians/Connacht)
IRELAND'S IRB JUNIOR WORLD CHAMPIONSHIP RESULTS:
Saturday, June 5: Ireland 22 France 25, Estadio El Coloso del Parque, Rosario
Wednesday, June 9: Ireland 21 England 36, Estadio El Coloso del Parque, Rosario
Sunday, June 13: Argentina 24 Ireland 21, Estadio El Coloso del Parque, Rosario