McIlroy, who won his second major title at the PGA Championship last month, adds significant celebrity power to the US$6 million event which is yet to announce next year’s title sponsor.
The Northern Irishman, as well as four-time major champion Mickelson, will also play a prominent role in the famous Ryder Cup team tournament taking place in Chicago later this month.
The November 8-11 Singapore Open, touted as “Asia’s major”, started in 1961 but is competing in an increasingly crowded market. In May, British bank Barclays decided not to extend its current contract, which expires this year.
Last month, Asian Tour chief executive Mike Kerr told AFP he was in talks to bring an “iconic” tournament at a “similar level” to the majors to Asia within three to five years, but did not reveal in which country.
McIlroy underlined his top ranking on Sunday when held off an elite field to claim his second consecutive win on the US PGA Tour play-off series, putting him in pole position for the series champion’s $10 million bonus.
The 23-year-old will play in Singapore as part of an Asian swing that will also take him to the BMW Masters in Shanghai and a one-day matchplay face-off against Tiger Woods elsewhere in China.
Australia’s Scott, the world number five, can burnish his season after a heart-breaking outing at the British Open, where he threw away a four-shot lead with four holes to play to hand victory to Ernie Els.
He will feel at home in Singapore after winning a record three titles in 2005, 2006 and 2010, and finishing third in 2007 and equal third in 2009.
Left-hander Mickelson is seeking his first win at Sentosa Golf Club after competing in the last five Singapore Opens. His best finish was in 2008, when he placed ninth.
A field of 156 will compete for the $1 million winner’s cheque at an event which is also known for its weather delays.
Last year, Spain’s Gonzalo Fernandez-Castano beat Filipino Juvic Pagunsan in a play-off which had to be completed early on the Monday morning after a series of tropical storms.