The 60-year-old Dutchman will return to the Amsterdam Arena next year as he joins the board of directors, which will include former midfielder Danny Blind
The 60-year-old was relieved of his duties on the bench by the Bundesliga side last season, but he is still under contract there.
Once his deal expires, he will move to Ajax, who have rearranged their board of directors.
Former player Danny Blind and Martin Sturkenboom are in line to complete the board as technical and financial director respectively, but this has yet to be confirmed by the club's members council.
Van Gaal returns to Ajax having enjoyed an illustrious past there.
He began his coaching career in Amsterdam in 1991 before leading the Dutch club to a Uefa Cup in 1992 and a Champions League three years later.
Van Gaal left his post as coach in 1997 but returned in 2003 as a technical director before departing again in 2004.