Mickelson, who became the GHO's first back-to-back winner last year, has committed to playing the tournament July 24-27, The Hartford Courant reported on its Web site.
'I have a very special place in my heart for the Greater Hartford Open,' Mickelson said in a statement released by the Greater Hartford Jaycees, whose sole fundraiser is the GHO. 'I love the support the community gives the event and the TPC at River Highlands.'
Mickelson birdied the 18th hole last year for a one-stroke victory over Jonathan Kaye and Davis Love III.
Love won the MCI Heritage on Sunday to move to the top of the PGA Tour money list with his third victory of the year.
Mickelson has five top-10 finishes in seven starts this year, including a third consecutive third in the Masters. He also is 15th on the money list with $967,975.
He has 21 tour victories and is third in career earnings, with $23.1 million, behind Tiger Woods and Love.