It is understood the former St Johnstone and Bristol City manager could be confirmed as the Dons' boss as early as Monday morning.
Current boss Craig Brown announced last Monday that he was retiring from management and would step aside immediately if the club found an instant successor.
Aberdeen reportedly had a move for Ross County manager Derek Adams rebuffed before agreeing a deal with McInnes - the details of which are set to be finalised.
McInnes led St Johnstone to promotion in his first full season before establishing them as a comfortable Clydesdale Bank Premier League club.
But he lasted just 14 months at Ashton Gate, taking the npower Championship club to safety in his first season but paying the price for their continuing struggles.
The former Morton, Rangers, West Brom and Dundee United midfielder was sacked in January after a 4-0 defeat by Leicester sent City to the bottom of the table.
The 41-year-old's first task at Pittodrie will be to try to earn the Dons a top-six spot.
Aberdeen sit in ninth place in the SPL and have won just once in 11 games in 2013, but they are only two points off the top half of the table with games against Hearts at home and Dundee United at Tannadice to come before the split.