When the final penalty was awarded to Ireland on Saturday, he raised his arms aloft, staring down at Jamie Heaslip clasping the ball in a ruck that had weary Australian captain James Horwill and Pat McCabe at the bottom of it.
The smile of satisfaction was broad for a man who had tears in his eyes when delivering some motivational words before kick-off.
It was far from being a perfect performance, but O'Connell recognised it as a considerable step towards Ireland reaching the quarter-finals of the tournament.
"(This performance) has always been there. The last six or seven weeks, we've probably been waiting for this game," he told ITV Sport.
"We talk the talk about taking every game as it comes, but this was always a big game in the back of our minds.
"Obviously a lot of motivation came from the disappointment of the last four or five weeks, in how we played and how we performed.
"We just didn't live up to our potential. You don't mind being beaten or whatever, but you hate not playing to your potential. At least today we played to our potential."
O'Connell has captained the Lions to a Test victory in the Southern Hemisphere and won a Grand Slam and two Heineken Cups. He agreed that beating the Wallabies away from home is 'right up there' as a career highlight.
The next challenge is to repeat this level of performance in next weekend's Pool C encounter with Russia, and he warned that Ireland cannot afford to rest on their laurels.
"We've won nothing, it's just a pool game. Obviously it's a special day, but this is the level we can play at and should be playing at consistently," insisted O'Connell.
"The fact that we've reached the level we're supposed to play at once shouldn't be a big deal really.
"They're all big games from now on in, we just need to make sure we put in that big performance each game now. Anything can happen."
The Limerick man, who will have a scan on a hamstring strain on Monday, also praised his fellow forwards for outplaying the Wallabies at set piece time and in the loose.
"We've a great back row. When you think that David Wallace is sitting at home as well...we've a phenomenal back row and phenomenal back-up in the back row.
"It just shows the strength in depth we have in the team. Our back row were outstanding, as were our front row. I think both units drove the team on today."
One member of the front row union who particularly stood out was Rugby World Cup MasterCard man-of-the-match Cian Healy.
It was a tournament debut to remember for the young Dubliner, a vital cog in a dominant Irish scrum and a player who put his body on the line in defence and attack.
"It felt good to dominate the Australian scrum. It's always nice to get on the front foot and load the pressure on," he said afterwards.
"I'm pretty happy about that. I'm really chuffed to have been named man-of-the-match. I didn't expect that.
"We have been working hard at scrummaging (with Greg Feek) and we knew it was coming. I wanted us to be dominant there because I know how hard it is for backs to play if they don't have that platform to work off.
"We'd done a fair bit of research into their scrum and everything had gone according to plan. It was enjoyable. It was a good pack performance. We clicked well."
An Under-20 Grand Slam winner in the year Ireland faltered at the last World Cup, Healy is focused on making sure the men in green back up this win with two more before the pool stages are completed.
"This is a great boost for us going forward. There are a few things we still have to work on but for now we'll enjoy this.
"I'm not looking at the other side of the draw yet, we still have two more pool games. We're going to need more big performances if we're to get further in the competition."
Follow the Ireland team in New Zealand on www.twitter.com/irfurugby.