And a clearly delighted Holley was full of praise for the togetherness and team spirit that ultimately saw the Ospreys through in a hard-fought yet entertaining encounter at the RDS.
"As somebody who has been to every Ospreys game, it's pretty much up there with the best of them," said Holley, who has been with the region since its inception in 2003.
"It's a special night. I wouldn't say it was our best performance but it was certainly one of our most courageous and determined.
"We went out to try and win it and to score tries and we did that. Not a lot of teams come here and score tries against Leinster so to score two in the first half gave us the belief to go on and win it.
"We were trying to lose it in the second half by giving away some penalties but our defensive effort in the end was outstanding."
The Ospreys ran out 17-12 winners after establishing a 14-3 half-time lead having scored two superb tries in the first period against a Leinster side who hadn't lost at home for 20 months.
Tommy Bowe's 39th Magners League score and his eighth in 16 games this season came after a subtle change of angle from outside centre Andrew Bishop, while Lee Byrne's 35th-minute effort followed a brilliant attacking move.
"We had a gameplan and a strategy which sometimes comes off and sometimes it doesn't," added Holley.
"We just felt that we could get through on our short pass in the midfield which resulted in our first try, and the second try down the short side was again something that we'd spotted.
"I'm particularly proud of our midfield tonight. James Hook is playing with a shoulder injury that is being operated on Wednesday and Andrew Bishop has just been a superb player for us this season, particularly in defence, and he was outstanding tonight.
"I'm not surprised that we broke through because we've got some real talent and when they get the bit between their teeth and things do come off then we can score tries. It hasn't quite happened in every game this season and we have bombed chances but we've taken the two most important ones tonight.
"It's about who performs better on the night and takes their chances and we were the ones that did that tonight."