- Ansu Fati (55')
Fati came off the bench at half-time and needed just 10 minutes to make his mark, cutting in from the left before curling into the top corner from just inside the box.
The Barca forward celebrated on the touchline with teammate Ousmane Dembele, who was left out of the squad as Barca negotiate his transfer to Paris Saint-Germain.
The win concludes Barca's tour of the United States after losing to Arsenal and beating Real Madrid in their previous two matches, while Milan return to Italy after defeat against Madrid and a draw with Juventus.
Maignan also kept out a rasping 25-yard strike from Raphinha and a far post header from Torres, although Milan also had their chances in the first half.
Barca made five changes at the break and it was one of them, Fati, who broke the deadlock after linking with the lively Alejandro Balde.
Pulisic suffered a scare minutes later after landing awkwardly following a challenge with Balde, but was able to play on, with Milan coming close to a leveller when Leao bent just over.
Oriol Romeu then headed wide for Barca and Araujo had a goal correctly ruled out for offside before both teams missed two great chances in the final stages.
First, Reijnders fluffed his lines after robbing Sergino Dest and playing a one-two with Leao, shooting wide from six yards, and then Fati, with the goal gaping, saw his effort blocked by young Milan defender Davide Bartesaghi.
- Alex Chilowicz