Roddick missed the O2 last season because of an injury
Andy Roddick completed the eight-man line-up for next week's ATP World Tour Finals in London as results went his way at the Paris Masters on Thursday.
The American beat Ernests Gulbis 6-3 7-6 (8-6) in round three to put Jurgen Melzer out of the running for London.
And Gael Monfils' victory over Fernando Verdasco ended the Spaniard's hopes.
Roddick will join Rafael Nadal, Roger Federer, Novak Djokovic, Andy Murray, Robin Soderling, Tomas Berdych and David Ferrer at London's O2 Arena.
The season-ending tournament for both singles and doubles gets under way on 21 November.
I think it's an honour to qualify once, and then each time I think kind of you realise how tough it actually is
Roddick will make his first appearance at the event since it moved to London last year, with the former world number one unable to compete 12 months ago because of injury, despite having qualified.
"I'm happy that I've won some matches and not so far relied on people losing," said the 28-year-old.
"That's kind of the attitude I had coming into this week and I think that's what I'm going to go with, as opposed to sitting around and hoping for people to lose.
"I think it's a goal at the beginning of every year. It's certainly an accomplishment every year. I think it's an honour to qualify once, and then each time I think kind of you realise how tough it actually is.
"You can't just play well for one week. It's the culmination of doing it week after week on tour."
Berdych will be the only player making his debut in the event, while defending champion Nikolay Davydenko and last year's runner-up Juan Martin del Potro will be absent after seasons interrupted by injury.
"Qualifying for London is the pay off for all the hard work during the year and I'm very happy to see my name among the best eight players in the world," said Berdych.
Verdasco and Jurgen Melzer were the only players still able to break into the top eight at the start of play on Thursday, but Verdasco went down 6-7 (4-7) 7-6 (7-2) 7-5 to Monfils after missing two match points, while Roddick's victory took Melzer out of the picture despite the Austrian's impressive 7-6 (8-6) 2-6 6-3 defeat of Ferrer.
"I'm a baseliner, so I prefer slower courts," said Ferrer. "I'm physically fit and it's a nice feeling to qualify for a second Masters Cup."
Highlights - Davydenko beats Del Potro in O2 final