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.
Parma started brightly with Sebastian Giovinco pouncing on a mistake only to fire over before Jaime Valdes ended a good run by shooting wide from the edge of the penalty area.
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.
Milan wrapped up the match in the 54th minute when Antonio Nocerino slipped the ball to Emanuelson on the counter-attack.
The Dutchman burst between two defenders, surged forward, slipped past goalkeeper Antonio Mirante and tucked the ball into the net for his second goal of the campaign.
Just to prove it was not Parma's night, Sergio Floccari struck the crossbar with a fierce volley in stoppage time.
