Officers are investigating an assault which occurred on Captains Road, Crumlin, at approximately 1.30am last night.
A 31-year-old man was taken to Saint James's Hospital after he and a second male were involved in an altercation with a group of other men.
His condition is described as serious. It is understood the man's injuries include extensive injuries to his face.
The second male was not seriously injured.
After the incident the group of men are believed to have fled the scene on foot in the direction of Armagh Road/Windmill Road.
Gardaí arrested a man in his mid 20s in connection with this investigation this afternoon.
He is currently detained at Crumlin Garda Station under Section 4 of the Criminal Justice Act, 1984.
Investigating Gardaí are appealing for witnesses or anyone with information to contact them at Crumlin Garda Station on 01 6666200, the Garda Confidential Line, 1800 666111 or any Garda Station.