Four men armed with hammers entered the house at Church Green in Holywood shortly after 8pm yesterday and assaulted the man.
The victim's injuries are not believed to be life-threatening.
A man in his 30s was later arrested.
Police also seized two cars for further examination.
Detectives are working to establish a motive for the attack.
Meanwhile, A 27-year-old man arrested in connection with a serious assault in Randalstown, Co Antrim, has been released on bail pending further inquiries.
The incident occured on Main Street early on Sunday morning.
A 20-year-old man remains in a critical condition in hospital.
