The popular Irishman broke his major duck a year earlier after seeing off the challenge of Sergio Garcia in a thrilling climax to proceedings at The 136th Open at Carnoustie.
And despite injuring his wrist eight days prior to his title defence, Harrington rose to the occasion once again at Royal Birkdale to retain his crown as Champion Golfer of the Year.
In his own words, Harrington relives his journey to becoming Champion Golfer, reflecting on his near misses and his two memorable title triumphs at The Open.
First chance at success
The youngest of five sons, Harrington’s relentless competitiveness was driven into him as a child as the brothers challenged each other for superiority in a wide range of sports.
He turned professional in 1995, having initially not been inclined to do so, and made his first appearance at The Open the following year at Royal Lytham & St Annes.
A top-20 finish on his debut suggested greater things to come – with the evidence becoming even more compelling in 1997 at Royal Troon, where he achieved a fifth-place finish.
But it wasn’t until Muirfield in 2002, aged 30, that Harrington had his first taste of competing for the Claret Jug – missing out on the four-man play-off by just a single shot.
“Muirfield in 2002 was the strangest week for me,” he said. “It was the first time I had a real chance of winning a major, winning The Open. I played phenomenal that week.
“Four days of the best tee-to-green golf I've ever had. I was gutted to miss out - and I was gutted because I could take nothing away from the week because I didn't know why I played well.
“To me it felt like an exceptional week, that I didn't feel I had control of or could repeat. As much as I had a chance of winning, I went away from it feeling that I needed to get lucky to a win a major.”
Harrington would have to wait another four years before he could realise his Champion Golfer potential – holding his nerve after almost missing out on the play-off again.
Carnoustie was the setting for The 136th Open – a course famed for Jean van de Velde’s dramatic collapse on the final hole in 1999 when he only needed doubled bogey to win The Open but triple bogeyed it and missed out to Paul Lawrie after extra holes.
“There’s no doubt Carnoustie is the toughest of the Championship courses we play,” Harrington said. “Every time you walk down that 18th hole, you look exactly where van de Velde hit his second shot.”
Sergio Garcia had appeared to be on course for a wire-to-wire win, before he faltered on Sunday allowing Harrington to stand on the 18th tee with a one-shot lead.
“I was really confident on 18 but I do think it is the hardest finishing hole in golf. I stood at the tee, really confident, burst it down there. I was buzzing and I hit an appallingly bad tee shot.
“I thought I'd lost The Open. The only time in my life I think I've ever been on the golf course and embarrassed. I would have been happy for the ground to open up and swallow me up.”
That winning feeling
Harrington went into the Barry Burn twice but salvaged a double bogey to finish with a round of 67, giving Garcia a one-shot advantage going down the final hole.
“Probably the utmost interesting thing from that moment on, was I sat watching Sergio come down the last and I kept saying to myself, ‘I'm going to win The Open’,” Harrington added.
“So when he missed and there's a playoff, I didn't feel like I was getting a second chance. I was in the same frame of mind I was before he hit the putt as I was afterwards.”
In the four-hole playoff, Harrington lead by two going into the 18th and a bogey proved enough for him to become the first European winner of The Open since Lawrie in 1999.
“It was exhilarating,” he said. “You've won The Open. It was something I dreamed about, for sure, to have done it was amazing. Like my name is etched in history.”
Remarkable injury recovery
Disaster struck Harrington before his Open defence when he hurt his wrist in bizarre circumstances during a practice session just hours after winning the Irish PGA Championship.
“Bearing in mind I'd won the tournament at about ten o'clock that night I was at home and I was doing some speed work,” Harrington explained.
"In my wisdom, I decided well, I'll do a one hander happy Gilmore into the impact bag and when it hit the bag I sprained my wrist. If it wasn’t the Open I would have pulled out.”
In testing conditions at Royal Birkdale, Harrington quickly realised his wrist would be okay and he grafted impressively to sit in joint-second going into the final round.
Only Australian legend Greg Norman, a two-time Champion golfer, stood in Harrington’s way after the 53-year-old rolled back the years to lead the way after three rounds.
“I played with Greg Norman on the Sunday and I feared that a lot,” said Harrington. “I'm not a sentimental person, but I was afraid that the golfing gods were going give him one for the road.”
Royal Birkdale brilliance
Norman ultimately faded with a final round of 77 as Harrington rose to the challenge, hitting a stunning approach into the penultimate hole from more than 240 yards to clinch the title.
“I was lying on a little down slope at the back of a knoll and I think, you know what, it's a left to right wind, it is blowing but five wood is my favourite club in the bag.
“I've just hit a couple of really nice shots with it. I feel great with this club. I'm going to take this on. I knew if I hit this shot, I was taking Greg Norman out of play.”
Harrington finished with a final round of 69 to win his second Claret Jug by two shots from Ian Poulter – and he admitted retaining his crown was almost cathartic.
“Carnoustie will forever be so exciting because it was my first major but there was always something wanting afterwards,” he said. “I'd messed the 72nd hole up.
“I'd left something behind. There was questions whether I should have won the tournament, whether I deserved to win the tournament, playing the holes the way I did.
He added: “Has it changed my life? Yeah, I would think it's changed my life. For as long as we go on there will be an Open Championship and my name will be on that trophy.”