Youngs, who made his first-team debut for Tigers this season, got on the end of a pass from Luke Cozens (Bath Rugby) in the final play of the game as England battered the Welsh line to end their U-21s Six Nations campaign in thrilling fashion.
Cozens kicked the conversion to level the scores and earn some reward for a comeback which seemed unlikely when Rhys Priestland kicked Wales into a 21-11 lead with his seventh penalty.
"All the team pulled together and said 'We aren't losing this' and it was a great effort," said Youngs. "It's a mixture of relief and joy I suppose - it's just a shame that we played our best rugby in the last 10 minutes. The forwards put in a great effort to get us into that position."
Youngs scored from centre after moving from wing - his first ever game there - and coach Nigel Redman said: "I would have given the ball to Tom Youngs all night. He ran with passion and pace, as if his life depended on it, and you have to commend him for that.
"It was probably a fair result, although that was a game we probably could have won. In the last 10 minutes they showed the tempo and the intensity that we have been asking for and coaching and when their backs were against the wall they showed what they could do."
England have won two, lost two and drawn one of their five Championship matches and captain Danny Care said: "Fair play to the lads tonight, they played for 89 minutes and showed a never-say-die attitude. We lacked accuracy which could have won us the game and we played our best rugby in the last 10 minutes."
Youngs was joined in the starting XV by Tigers colleagues Dan Cole and Alex Shaw, while a fourth Tiger, wing Ollie Dodge, appeared as a 65th-minute replacement.
Wales U-20s:
M Thomas (Dragons); A Jenkins (Llanelli/Scarlets), J Lewis (Bedwas/Dragons), G Maule (Newport/Dragons), J Norris (Bedwas/Dragons); R Priestland (Llanelli/Scarlets); R Lewis (Neath/Ospreys); H Gustafson (capt, Llanelli/Scarlets), M Jones (Sale Sharks), J Corsi (Newport/Dragons), B Davies (Blues), J Down (Cardiff/Blues), D Lydiate (Ebbw Vale/Dragons), J Harris (Bedwas/Dragons), L Evans (Newport/Dragons)
Replacements:
K Owens (Llanelli/Scarlets) for Jones 65, N Eaves (Pontypridd/Blues) for Gustafson 72, M Larsen (Cardiff/Blues) for Evans 75, D Allinson (Cardiff/Blues) for R Lewis 59, R Jones (Sale Sharks) for Priestland, L Ford (Wanderers/Blues) for J Lewis 74. Not used: A Brown (Bedwas/Dragons)
Pens: Priestland 7
England U-20s:
D Smith (Northampton Saints); D Doherty (London Wasps), D Waldouck (London Wasps), A Powell (Saracens), T Youngs (Leicester Tigers), L Cozens (Bath Rugby), D Care (NEC Harlequins, capt); D Cole (Leicester Tigers), M Mullan (Worcester Warriors), T Mercey (Saracens), D Attwood (Bristol Rugby), P Hoy (Northampton Saints), A Shaw (Leicester Tigers), A Saull (Saracens), H Ellis (London Wasps)
Replacements: R McMillan (Gloucester Rugby) for Mullan 54, C Beech (Northampton Saints) for Cole 54, C Pennycook (Bristol Rugby) for Saull 65, M Cox (Worcester Warriors) for Shaw 75, D Pointon (Northampton Saints) for Care 76, O Dodge (Leicester Tigers) for Smith 65
Not used: B Thomas (Saracens)
Tries: Doherty, Youngs Pens: Cozens 3 Con: Cozens
