The brutal attack happened in Whinfield Walk in Carrickfergus last night.
Detective Inspector Lyle said: “It was reported that at around 10pm a number of masked men forced their way into a house in the area and assaulted the 19 year old male occupant with baseball bats and a hammer.
“The victim has sustained a number of serious injuries and is currently receiving treatment in hospital.
“I am appealing for anyone who witnessed the incident or anyone with any information that can assist with the investigation to contact detectives in Ballymena on 101 quoting reference 1427 29/07/18.
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.”