The attack happened in the Woodbrook Avenue area of Lisburn.
Detective Sergeant Melanie McGrory said: “The 36 year old male was arrested in the Lisburn area yesterday, Monday 06 May.
“He was interviewed and subsequently released on police bail pending further enquiries.
“A 32 year old man suffered lacerations to his head after three men gained entry to his flat and assaulted him with a claw hammer around 11.30pm.
“Our enquiries are ongoing and we continue to appeal to anyone who witnessed the incident or anyone with any information that can assist with the investigation to contact detectives in Lisburn on 101, quoting reference number 1657 of 05/05/19.
“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.”