Owen Farrell kicked four penalties as England won a ferocious encounter 12-6 and passed what Lancaster rated as one of the biggest tests of their character.
“I am delighted to get the win here today,” said Lancaster.
“When you have the conditions as they were it was going to be a tight game and down to small margins.
“To come here with a young side and show that kind of maturity to close the game out was hugely pleasing.
“It is a very difficult to play rugby against experienced players when we have lads on single figures in terms of caps, it is great testament to their maturity.
“As a test of character it was right up there because of the quality of the Ireland side and the ability to get the win.”
Under incessant rain, it was what Lancaster calls England’s “warrior spirit” which shone through in a game of brutal intensity.
Ireland enjoyed most of the first-half possession but England defended like rabid dogs at times and they led 6-0 at the interval.
Ronan O’Gara landed two penalties to draw Ireland level and with, James Haskell in the sin-bin, England were suddenly up against it.
But England maintained their composure and won that 10-minute period, with Farrell restoring their six-point advantage.
“I put that up there as an absolutely massive win, a huge win,” said assistant coach Andy Farrell.
“We have come to Ireland and we have played against a very good Ireland side.
“There was a tricky point in the third quarter but the way we composed ourselves and finished the game – our energy got better, our line speed got better, our composure – was a masterclass of how to handle that last 20 minutes.
“For a young side to play like that in a pressured situation against a team that has been there and done that, and been successful with it, is a credit to everyone.”
Two years ago on their last Six Nations visit to Dublin, England failed to match Ireland’s intensity and their grand slam ambitions were demolished at the Aviva Stadium.
Yesterday, they refused to take a backward step to become the first English side to win a championship game in Ireland since Martin Johnson’s grand slam team of 2003.
“The lads were desperate for the victory,” said forwards coach Graham Rowntree.
“Coming into the Six Nations we had to back up that performance against New Zealand. We did that last week and then we had to do it away from home, because that defines you as a group of players.
“Going forward it will be fantastic to get that under their belts. They upped their game because they knew it would be a massive challenge.”
Haskell was relieved his second-half sin-binning did not cost England – but he had feared it might.
Haskell was shown a yellow card for kicking the ball out of a ruck just as Ireland were beginning to crank up the pressure and O’Gara kicked the penalty to bring the scores level at 6-6.
The sin-binning proved to be a turning point – but in England’s favour because they won that 10-minute period 6-3 with Owen Farrell kicking two more penalties.
“I think my life probably flashed before my eyes (when I was yellow carded),” said Haskell.
“I thought if we lost the game I would have to run straight out of the stadium!
“I was disappointed it was a yellow card. I didn’t intentionally kick it but it was the third penalty in a row and someone was going to get it.
“The fact we won that period is credit to those on the field. It could have gone the other way, especially in Ireland against that quality of opposition but the boys dug really, really deep.
“I was just glad I got the opportunity to go back on. That victory was very big.”
Chris Robshaw, the England captain and man of the match, said: “We are always fired up and the message today was ‘no backward step’, whether it is little off-the-ball stuff or going after them from minute one and we did that today.
“We came here to put a marker down and we will build on that.
“We knew we hadn’t won here in 10 years and we knew why. Today we got it spot on.
“It was all about defence at the end of the day and someone like Owen kicking the goals. That performance was definitely right up there.”
Owen Farrell added: “If you practise enough it is only another kick and it’s no different in the stadium. It was a massive game and I’m really exited to come over here and get stuck into the game. The conditions weren’t great but we rolled our sleeves up and got stuck in.”