His body was found at an apartment on the South Circular Road, with a second man found injured on the street nearby.
Gardaí don't want to release the name of the man until all his family have been notified.
They say they've spoken to the second injured man – who's believed to be a Swiss National.
He's in hospital recovering from non life threatening injuries.
Superintendent Kevin McMeniman says they're carrying out further investigations this afternoon.
Gardaí are anxious to speak to a third man who was spotted leaving the scene yesterday.
He's described as 5 foot 6 in height, of thin build with fair hair.
He's not being treated as a suspect at the moment but officers believe he can fill in the blanks on what happened.
They're asking that man, or anyone with information, to contact them here at Kevin St Garda Station.
