The 15-year-old girl had been hanging out with a 16-year-old boy in Willoughby, on the Lower North Shore of Sydney, about 10.50pm, when they got into an argument with another couple.
The fight escalated and the girl was slashed and cut on her legs and sustained a serious laceration to the back of her head.
Her friend was allegedly punched in the head before his phone was stolen.
The vicious attack occurred just 100 metres from the Channel 9 Headquarters in Willoughby.
Police and ambulance crews were called to the scene, where they found the young girl seriously hurt.
She was treated on site before she was taken to Randwick Children’s Hospital, where she remains in a stable condition this morning.
The boy returned to the scene shortly after to help police with their investigation.
North Shore police are now searching for the couple responsible for the attack and have asked members of the public to come forward with any information from Friday night.