The three golfing powerhouses, along with a wealth of other marquee names, will compete in the US$6 million event at Sentosa Golf Club from November 8 to 11. Their sights will be set on the US$1 million winner's cheque.
McIlroy will arrive in the Lion City on the crest of a wave having claimed the U.S. PGA Championship in August which allowed him to regain top spot on the Official World Golf Ranking.
It was his second win in a Major championship after his success in last year's U.S. Open.
The 23-year-old won both titles by a staggering eight shots and his explosive driving and deft touch will no doubt be in full effect at the Barclays Singapore Open "“ which will be joint-sanctioned by the Asian Tour and European Tour.
He played in the tournament in 2008, a year after turning professional, and finished joint fourth.
On Sunday, he emphatically cemented his position as the world's top golfer by winning the BMW Championship for his third victory in four outings on the U.S. PGA Tour.
Scott has made Singapore's national Open his very own having won it a record three times in 2005, 2006 and 2010. He was also third in 2007 and equal third in 2009.
The world number six came narrowly close this year to winning his first Major when he led the Open Championship by four strokes with four holes to play but lost by a single stroke to South African Ernie Els.
Four-time Major winner Mickelson has competed in the last five Barclays Singapore Opens with his best finish coming in 2008 when he came in ninth.
With three U.S. Masters titles to his credit plus one U.S. PGA Championship, he will be eager to finally conquer Sentosa's famous Serapong Course.
"I am delighted that the 2012 Barclays Singapore Open will once again welcome the world's best golfers. Rory McIlroy, Adam Scott and Phil Mickelson are some of the most sought after players in the game and their presence will further enhance one of the world's premier tournaments," said Quek Suan Kiat, Country Manager and Chief Operating Officer of Barclays Bank PLC, Singapore.
A total of 156 players will complete including 63 from the Asian Tour and 63 from The European Tour. There will be 10 sponsor invites while three spots will go to amateurs nominated by the Singapore Golf Association and three places made available to professionals selected by the Singapore Professional Golf Association who are not otherwise exempt.
A qualifying tournament will be held on Sunday, November 4 on The Serapong Course where the top three finishers will progress to the main event.
"This year marks the 49th staging of the Singapore Open and thanks to Barclays and Sentosa everything is once again in place for Asia's showpiece golfing event. The Singapore Golf Association are the guardians of our national Open and we are proud that it now ranks as one of the world's premier events," said Bob Tan, President, Singapore Golf Association.
"The Barclays Singapore Open continues to set new standards for golf in the region, which is something that it has always done since its inauguration. With a list of past champions that dates back to 1961, the Singapore Open has earned its place in the history books as a tournament that helped build the foundations for the development of tournament golf in Asia," added Tan.
For the past two years, Sentosa's Serapong and Tanjong Courses have been used for the tournament but this year, only the former will be used.
"This is the eighth year the Singapore Open is being held at Sentosa Golf Club and we are excited to continue attracting some of the world's greatest golfers to The Serapong course," said Low Teo Ping, President of Sentosa Golf club. "The team is priming the character of the rough, the shape of the fairways and raising the mowing height to challenge their golfing skills and talent."
Spaniard Gonzalo Fernandez-Castano triumphed in the Barclays Singapore Open last year after he pipped Filipino Juvic Pagunsan to the title by draining a 10-foot birdie putt on the second playoff hole on Monday.
The duo ended the weather-shortened tournament tied on 14-under-par 199 after the third and final round on Sunday but thunderstorms thwarted attempts to finish the playoff.
When play finally resumed early on Monday morning, it was the 31-year-old Spaniard who got the better of the man from the Philippines on the second playoff hole. Both players are expected to return this year.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.