The 23-year-old, who cost £7.5m when he signed from Udinese in the summer, was sent off three times in Serie A last season.
Now Fratton Park boss Redknapp has been forced to take his star to one side and read the riot act.
He said: "We need to Sulley to stay on the pitch - and I have told him that. He's a naturally aggressive player and we don't want him to lose that from his game.
"But he has to learn that there are certain situations where he has to just walk away and not get involved in any nonsense."
But despite Muntari's disciplinary troubles, Redknapp believes he has a real star on his hands.
He added: "I bought Sulley because he has got as much potential as anyone I've seen for a long time. He needs to get himself into his own place because he's still living in a hotel.
"But once he gets settled we'll start to see what he can do."