Originally reported as a possible stabbing, police have said they are working to establish the cause of the injury.
A 40-year-old man from Hove is being treated at Royal Sussex County Hospital and his condition is not being described as life-threatening.
No arrests have been made.
A spokesman for Sussex Police said: "At 11.30am on Saturday (4 July) police were called to an address in Portland Road, Hove, after a 40-year-old man living there had sustained a head injury.
"He is being treated at the Royal Sussex County Hospital where his condition is not described as life threatening. An investigation is under way to establish the cause of the injury and the full circumstances. There have been no arrests at this stage."