A brilliant individual goal by Urby Emanuelson, who ran from just inside his own half to score, completed the win early in the second half.
Milan, missing Robinho, Mark van Bommel, Kevin-Prince Boateng, Ignazio Abate, Clarence Seedorf, Alessandro Nesta and Alexander Pato, moved on to 60 points from 28 games.
Roberto Donadoni's Parma are 17th with 31 points, although they are still six clear of the relegation zone.
Milan won a penalty with their first real attack when Emanuelson's shot hit Cristian Zaccardo's arm and Ibrahimovic, Serie A's leading scorer, made no mistake from the spot.
Parma's misfortune in front of goal continued as Gabriel Paletta's header bounced off Thiago Silva and struck the bar. However Milan were by now creating plenty of chances of their own with Stephan El Shaarawy hitting the post.
Just to prove it was not Parma's night, Sergio Floccari struck the crossbar with a fierce volley in stoppage time.
