An Irish Rail worker was severely injured when he was attacked by three men at Connolly Station on Saturday morning at 8:30 am.
The group of men became aggressive when the male Irish rail worker asked them about a dog they had brought into the station.
According to Dublin Live, the worker was assaulted and left seriously injured when he asked them to leave.
Gardaí arrested three individuals who were later released with a file sent to the DPP.
The Gardaí are continuing to investigate the incident.
No weapons were used in the attack.
A garda spokesperson said: "Gardai in Store Street are investigating an assault which occurred at a train station on Amiens Street Dublin 1 on Saturday the 21st of July 2018 at approximately 8.30 am."