Going into the final day, Ireland were one of three sides in with a realistic chance of clinching the crown and first watched on as Wales thumped Italy 61-20 in Rome, piling the pressure on Ireland, who had to beat Scotland by at least 21 points to move ahead on points difference.
O'Connell's men delivered thanks to a 20-0 second half at Murrayfield that saw them run out 40-10 winners and move 10 points ahead of Wales in the standings.
England started the day four points clear of Ireland, so had to overcome France by 26 points to steal the title and they were desperately close to doing so, but could only record a 55-35 triumph to fall six short.
Speaking after his side had been confirmed as champions for the second straight year, O'Connell told reporters that it was like being a powerless supporter watching the action at Twickenham.
He said: "When you're playing in a match and you're trying to win it, like we were in the Stade de France last year, you're just focusing on the next moment or whatever happens next. The scoreline and all that is probably your only focus and when you're in the heat of the battle those nerves and those feelings, they don't come into it.
"When you're sitting there at a table with a few of the lads and a beer in front of you watching on TV, it's like being a supporter - you're completely powerless as to influencing the result. It was just such a bizarre day.
"Even the crowd afterwards and the music, it was like Robbie Henshaw's 21st birthday there with the 80s hits coming out!"
O'Connell, on the day that he earned his 101st cap, scored their opening try at Murrayfield inside five minutes to set them on their way.
Had the Scottish full-back gone over and the try been converted, Ireland would have ended up one point shy of England and not won back-to-back titles for the first time since 1949.
When asked if he felt Ireland were lucky over the course of the day, O'Connell said: "I've been involved in plenty of games where the rub of the green has gone against us, but Jamie's tackle today was an incredible piece of skill. I wouldn't put it down to luck.
"But I suppose a lot of things did happen for three games to go like that and for us to come out on top, maybe someone was smiling down on us. I don't know."
At 35 years and 152 days old, O'Connell became Ireland's oldest ever captain in what could be his last Six Nations game.