ABC News reported the first lady's office confirmed an official announcement will be made Tuesday.
President Barack Obama fired McChrystal last year as commander in Afghanistan when disrespectful remarks were reported.
The general is to lead an advisory board for Michelle Obama and Jill Biden's Joining Forces initiative. The program will be run by the private Center for a New American Security along with the first lady's office.
Biden is the vice president's wife.
"I'm so proud that General McChrystal will continue to serve our country through this critical effort. … This program will build upon our nation's great patriotism by asking all Americans to take action and ensure our military families have the support they have earned," the first lady's statement said.