Officers allege the accused (17) was at an out-of-control party in Marangaroo and part of a large group of youths who attacked a 16-year-old boy in the street on Westgate Way on December 19.
The victim was taken to Joondalup Health Campus before being transferred to Royal Perth Hospital with critical injuries.
Acting Senior Sergeant Bruce Bowers said the victim spent several days in the intensive care unit.
“He needed surgery to relieve pressure on the brain… we were quite concerned,” he said.
He said the victim’s condition had since improved.
Police charged the man with aggravated grievous bodily harm and assault occasioning bodily harm on January 3.