The victim sustained his injuries following an altercation with a group of men.
Gardaí are investigating an incident of assault that took in place in Dublin city centre in the early hours of Sunday morning (3 November).
A man in his late 20s received head injuries following a reported altercation with a group of males in the O’Connell Street Upper area at approximately 1.15am.
The victim was subsequently taken to the Mater Hospital in a serious condition.
No arrests have been made and investigations are ongoing.