Officers are cracking down on loitering youths after bringing in new powers to break up groups.
The dispersal zone in the Windmill Park Estate will run until April 9 and police hope it will cut down noise, littering, criminal damage and street drinking in the area.
Brought in by the Norwood Green Safer Neighbourhood Team, it gives them and other officers the power to force people in groups to leave the area, as well as tell individuals who do not live there to move on.
Anyone under 16 years old is banned from entering the zone between 9pm and 6am unless accompanied by an adult guardian.
The area runs from Windmill Lane in the west, to Uxbridge Road in the north, along the borders of the former St Bernard's Hospital in the east, to Navigator Drive in the South.
Superintendent Ian Jenkins said: "Any individuals, regardless of their age, seen to be acting in an anti-social manner will be dealt with.
"Everyone has a right to feel safe in their community."
Anyone caught returning to the area after having been moved on by police faces a hefty fine or a prison sentence.
