A man with stab wounds to his neck and chest was found by police who were called to a unit black in South Granville over night.
Police said they responded to a call about 8.15pm and found the 46-year-old victim with severe wounds at a unit block on Chiswick Road.
He was taken by ambulance to Westmead Hospital for treatment.
Police said his wounds appeared to be non-life threatening.
A crime scene was established and examined by forensic specialists.
A 40-year-old man was arrested at the scene and taken to Merrylands Police Station, where he assisted police with their inquiries.
He was later released without being charged.