Perth City Detectives have charged a 26-year-old Ocean Reef man over an assault on a 21-year-old Mullaloo man early on Sunday.
WA Police allege a fight occurred outside a nightclub after clubbers were kicked out.
A police spokeswoman said it would be alleged that "at around 3am, an incident occurred inside a Murray Street nightclub which resulted in a number of patrons being evicted.
"An altercation then occurred between the victim and the alleged offender outside the club, with the victim falling to the ground and striking his head.
"He was rendered unconscious and remains in Royal Perth Hospital with serious head injuries."
The police spokeswoman said the alleged offender was also hurt and was treated at Sir Charles Gairdner Hospital for a fractured eye socket.
The accused man has been charged with Grievous Bodily Harm and will appear before the Perth Magistrates Court today.