Jonathan Afolabi netted an equaliser from close range only for Jim Crawford’s team to go ahead seconds later through an own goal by Morgan Boyes.
Crawford handed starts to seven U21 debutants in Wales; Brain Maher, Mason O’Malley, Luca Connell, Conor Noss, Louie Watson, Andrew Omobamidele and Alex Gilbert.
It was the hosts who struck first in the 11th minute through Joe Adams. Niall Huggins received a wide cross-field ball, beat his man and squared it to Adams who finished first time.
Ireland composed themselves and looked to penetrate the Welsh defence but the home team remained difficult to breakdown.
An Alex Gilbert free-kick flashed across the goal but it was a half of few chances for the visitors and despite growing strong before the break, they went in trailing 0-1.
In the second half, Ireland came out on the front foot.
They had a glorious chance on 52 minutes when Watson put through Lee O’Connor but the captain couldn’t beat substitute Stevens in the Wales goal.
Tyreik Wright and Gavin Kilkenny were introduced after 68 minutes, replacing Mason O’Malley and Alex Gilbert respectively.
The game turned on its head in the 75th minute. Conor Noss weaved his way into the box and squared it to Afolabi to tap home from close range for a goal Ireland’s play deserved.
Two minutes later the game was turned around. Wales defender Morgan Boyes played the ball back to his own keeper but the ball carried and went in giving Ireland the lead.
Ireland went looking for a third. Grant and Will Ferry combined well down the left with Ferry squaring it to the Afolabi whose first time effort was left wide of the post.
Ethon Varian and Conor Grant then came on for their Under-21 debuts replacing Afolabi and Watson.
As the game drew to a close Ireland were able to soak up the pressure from Wales and saw the match out to record the win.
Speaking after the game Jim Crawford said: “I thought we were great in the second half. We were really positive and players weren’t afraid to get on the ball.
“We scored a decent goal to equalise and it was an unfortunate own goal for Wales but today was about seeing that the players could do it at this level and the players showed that.
“What a victory does is it builds confidence and it builds morale, the lads are extremely happy with the performance and so they should be, they should be proud. It sets us nicely for the June window.”
Wales: Webb (Shepperd, 46); Stevens, Sass Davies, Boyes, Eddy Jones, Stirk, Taylor (C), Huggins, Adams (Colwill, 81), Spence (Pearson, 61), Jephcott. (Norton, 61)
Unused Substitutes: Vale, Hughes, Colwill, Collins, Bowen, Beck, Margetson,
Republic of Ireland
Maher (GK); O’Connor, McGuinness, Omobamidele, O’Malley (Kilkenny, 68); Connell, Noss, Watson (Grant, 73); Ferry, Gilbert (Wright, 68), Afolabi (Varian, 86)
Unused Substitutes: Blair (GK), McEntee, Flynn, Richards, Lyons, Devoy,
Referee: John Jones (WAL)