Ibrahimovic continued his rich vein of form since moving across the Mediterranean from Barcelona in the summer, accounting for five of the last six goals scored by the Rossoneri, and all three goals in their two Champions League matches so far.
Former Ajax player Clarence Seedorf proved the playmaker in the 37th minute looping the ball into the box for the onrushing Ibrahimovic to control on his chest and blast into the roof of the net to level the scores at 1-1.
"It felt great actually and nice to score a goal. I have scored so many goals here so it is fun to be back," the Swedish ace told broadcaster Viasat after the match.
AC Milan had fallen behind to a goal from Mounir El Hamdaoui, after some sublime build up play by strike partner Uruguayan Luis Suarez, and were outplayed at times by a young and technical Ajax team.
Brazilian striker Robinho, who had been preferred to compatriot Ronaldinho in attack, missed a straightforward one on one with Ajax goalkeeper Marten Steekelenburg, before Ibrahimovic popped up to show Milan the way forward.
Steekelenburg was called into action again late in the second half when Kevin Prince Boateng smashed a cross from Ibrahimovic across goal only for the Ajax keeper to pull off a fine reflex save and force the ball out to safety.
The game played out 1-1, a fair reflection of the day's action and leaving Milan two points adrift of group G leaders Real Madrid who sealed a late 0-1 win against a hapless Auxerre, courtesy of an Angel Di Maria goal.
Zlatan Ibrahimovic moved to Ajax from Malmö in 2001 and went on to score 43 goals in 99 matches before moving to Juventus in 2004. His goal in the Amsterdam Arena is his first against a former club and makes him only the second player in Champions League history to score goals for five different teams.