Scorers: Ireland: Tries: Niall Annett (Ulster), Andrew Boyle 3 ((Leinster), Eoin Griffin (Connacht); Cons: Noel Reid 3 (Leinster); Pens: Noel Reid 2 (Leinster)
Samoa: Try: Tony Keresoma; Con: Karl Maleilegaoi; Pen: Patrick Fa'apale Faleono
Winger Andrew Boyle crowned his debut at this level with a hat-trick of tries as the Ireland Under-20s cut loose in the second half, pulling clear of a Samoan side that lost three players to the sin-bin.
Head Coach, Allen Clarke made nine changes to the team that lost out to hosts Argentina last time out, and one of those, out-half Noel Reid, nudged the Irish ahead through a third minute penalty.
His opposite number Patrick Fa'apale Faleono quickly replied but missed two further penalty efforts while Ireland, dominating possession and creating early chances, managed to forage ahead.
Reid kicked his second penalty and full-back Andrew Conway missed a try-scoring opportunity when he knocked on, but Ireland soon managed to breach the Samoan line.
They won a penalty off a scrum, Reid dispatched the ball to touch and with number Munster No 8 Paddy Butler central to an advancing maul, hooker and team captain Niall Annett managed to muscle over for a converted try.
Replacement hooker Tony Keresoma's try, which was converted, got Samoa back in touch but it proved to be their only try of a game which the Irish pack was controlling.
The Samoans lost their discipline and shape in the second period as they came under increasing pressure from the fresh-legged Irish. A try just before the break from the fleet-footed Boyle had provided an extra spurt for his side at 18-10.
With prop Joe Sililoto (late tackle) and number 10 Fa'apale Faleono (professional foul) yellow carded in quick succession, in the opening seven minutes of the second half, Ireland took advantage.
They got the nudge on at scrum time, Butler barged forward off the base and a bullet-like pass from Reid helped Boyle to scoot in for his second try. Reid's successful conversion made it 25-10.
The Samoans, who pipped Ireland to seventh place at last year's tournament, defended manfully until scrum half Jonathan Malo was sin-binned in the 73rd minute.
A brace of late tries from replacement centre Eoin Griffin and Boyle, with the pair exchanging assists, wrapped up a morale-boosting victory for the reigning Six Nations champions.
The result sets up a 9th-10th place play-off between Ireland and Scotland in Parana next Monday (12pm local time/4pm Irish time).
Speaking afterwards, Allen Clarke said: "It was important for us as a group to get a win. We've played some good rugby in the tournament and were on the end of three defeats in a tough group. We had a young side out there - eight of this side are Under-19s and are available for next season, and that bodes well for the Under-20s in 2011. Today was about getting the first win which ensures our existence in (this tournament) for next year, and all credit to the side. The scoreline certainly didn't flatter us. We've got Scotland in our final game. We'll go about our business as professionally as ever, we'll do our work on Scotland as I'm sure they will on us. We'll look at our defence and our opportunities to attack."
TIME LINE: 3 minutes - Ireland penalty: Noel Reid - 3-0; 5 mins - Samoa penalty: Patrick Fa'apale Faleono - 3-3; 15 mins - Ireland penalty: Noel Reid - 6-3; 16 mins - Samoa penalty: missed by Patrick Fa'apale Faleono - 6-3; 26 mins - Ireland try: Niall Annett - 11-3; conversion: Noel Reid - 13-3; 26 mins - Samoa penalty: missed by Patrick Fa'apale Faleono - 13-3; 28 mins - Samoa try: Tony Keresoma - 13-8; conversion: Karl Maleilegaoi - 13-10; 36 mins - Ireland try: Andrew Boyle - 18-10; conversion: missed by Noel Reid - 18-10; 39 mins - Samoa penalty: missed by Karl Maleilegaoi - 18-10; Half-time - Ireland 18 Samoa 10; 44 mins - Samoa yellow card: Joe Sililoto; 47 mins - Samoa yellow card: Patrick Fa'apale Faleono; 47 mins - Ireland try: Andrew Boyle - 23-10; conversion: Noel Reid - 25-10; 73 mins - Samoa yellow card: Joe Malo; 75 mins - Ireland try: Eoin Griffin - 30-10; conversion: missed by Noel Reid - 30-10; 77 mins - Ireland try: Andrew Boyle - 35-10; conversion: Noel Reid - 37-10; Full-time - Ireland 37 Samoa 10
IRELAND: Andrew Conway; Andrew Boyle, Brendan Macken, David McSharry, Simon Zebo; Noel Reid, Michael Heaney; Bryan Cagney, Niall Annett (capt), Martin Moore, Brian Hayes, Ben Marshall, Jordi Murphy, Brian O'Hara, Paddy Butler.
Replacements used: John Cooney for Heaney (half-time), David O'Callaghan for Marshall (48 mins), Dominic Ryan for Butler (53), Eoin Griffin for Macken (61), David Doyle for Annett (66), James McKinney for Conway, Denis Buckley for Cagney (both 68).
SAMOA: Sani Niue; Tulolo Tulolo, Matthew Gandy, Karl Maleilegaoi, Tito Sufia; Patrick Fa'apale Faleono, Jonathan Malo; Joe Sililoto, Ausetalia Vaiomanu, Frank Fa'atau, Joshua Tyrell (capt), Steven Luatua, Jeremiah Aloalii, Iosefa Timu-Sa, Joe Tupe.
Replacements used: Tony Keresoma for Vaiomanu (23 mins), Fred Tuua for Tulolo (49), Suamalie Tuiletufuga for Keresoma (57), Iopu Iopu for Timu-Sa (70), William Mateai for Niue (75). Not used: Gody Schuster, Vaiofaga Simanu.
Referee: Jaco Peyper (South Africa)