The body was found at about 6pm in an abandoned building on New Street in Waterford City. It’s understood the man, thought to be in his 20s, suffered head injuries.
The scene was sealed off while the body remained at the scene where it was kept over night.
A team from the Garda Technical Bureau is expected to carry out an examination this morning while a postmortem will be performed.
The property was formerly used as an arts building by Waterford Institute of Technology, close to Stephen St and Newgate St in the city.
Detectives are keeping an open mind and say the man may have been assaulted or may have suffered a fall.
Gardaí were last night trying to establish the identity and exact age of the man and have appealed for witnesses to contact the station in Ballybricken at 051-305300.