A woman was found unconscious below an apartment block at Telopea after plunging four metres from a unit into the grass on Wednesday evening.
A CareFlight helicopter flew to the woman's aid in Eyles Street following a triple zero call shortly before 8pm and she was treated by a trauma team and paramedics.
The 36-year-old suffered facial and head injuries.
She was taken to Westmead Hospital in a serious but stable condition.
Police are continuing to investigate the incident.