The world’s No. 2-ranked player skipped the event a year ago but will be making his 11th appearance in the tournament at Muirfield Village Golf Club, which runs from June 3-6.
Mickelson has two top-10 finishes in his previous trips to the Memorial.
The addition of Mickelson gives the tournament nine of the top 10 money-winners on the PGA Tour.
Tiger Woods, a four-time winner of the Memorial, has yet to commit to this year’s event after withdrawing from The Players Championship last week with a neck injury.
Tim Clark, who won The Players Championship, also said he’ll play the Memorial.