The body of the man was found a 2.35am on Monday at an address in Longate, Peterhead, Grampian Police said.
The death is being treated as unexplained and enquiries are ongoing.
Police said 30 officers were working on the investigation and appealed for anyone with information to come forward.
Detective Chief Inspector David Hadden, who is leading the investigation, said: "I realise that police activity in the Longate area will be causing some disruption to local residents.
"Please be reassured that it is our aim to return the street to normality as soon as possible.
"Aberdeenshire divisional staff and other specialist force resources have been deployed in order to bring this to a conclusion.
"There are in excess of 30 officers and staff working in the area currently.
"I am extremely grateful for the support and understanding being shown by householders and the wider community.
"Thankfully, incidents like this are uncommon in Peterhead and I would like to reassure the public that Grampian Police is fully committed to keeping our local communities safe from crime."