Gardaí are investigating all of the circumstances surrounding the discovery of a body in Drumcondra on Saturday.
The deceased, a man in his late 20s, was discovered by gardaí in an apartment on Achill Road yesterday evening.
The body remains at the scene which is being preserved for forensic and technical examination.
Investigating gardaí have also sealed off an area of Griffith Park, Drumcondra.
A man, aged in his 30s, has been arrested and is being detained at a north Dublin garda station where he can be held for up to seven days.
The office of the State Pathologist and Garda Technical Bureau have been notified and a post-mortem will be carried out.
An incident room has been established at Ballymun Garda Station and enquires are ongoing.