Police were called to Kariong, west of Gosford, just after 11pm yesterday.
They found a 13-year-old boy with a stab wound to his chest.
Officers were told the boy was wounded in an altercation.
Local residents performed CPR on the boy before emergency services arrived.
“I was here when it happened,” a young witness said.
“Tried my best to give him one more breath, two more breaths. But I guess it was just too late.”
Another young witness said: “Didn’t really deserve it. All over nothing. We lost him.”
Paramedics performed CPR for 40 minutes in a desperate bid to save the teenager.
The teen was airlifted to Gosford Hospital in a critical condition but died a short time later.
Police allege the two 13-year-olds met on the quiet suburban street for a prearranged fight.
It is also alleged one of those boys brought a kitchen knife from home.
A 13-year-old boy was arrested at a nearby home and has since been charged with murder.
He will face court today.
Neighbouring residents are shocked by the incident.
“I still can’t believe it’s happened. Like right across the road and the boy used to play with my son,” a neighbour said.