A man in his 60s was found lying on the floor of his home in the Rathcoole Drive area of Newtownabbey, having suffered extensive bruising to his head, chest, abdomen and limbs.
He was treated by paramedics at the scene before he was taken to hospital, where he remains in a critical condition.
Detectives are appealing for information.
Detective Sergeant Perks said: “We were contacted by Northern Ireland Ambulance Service, just after 7pm on Wednesday, who requested our attendance.
“The male occupant, who was found lying on the floor, was treated by paramedics at the scene and later transported to hospital, where he remains in a critical condition.
“The man, aged in his 60s, has sustained extensive bruising to his head, chest, abdomen and limbs.
“I am appealing to anyone with information, or who noticed any suspicious activity, to contact us on 101 quoting reference number 1841 of 03/06/20.”
Information can also be provided to Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org.