The incident occurred shortly after midnight on Friday, August 12.
Footage shows two men exchanging heated words before one man punches the other to the ground.
Once the man falls, the attacker continues to punch the victim in the upper body, and soon begins to kick him.
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A shrill scream can be heard as a woman jumps in to try and help the man receiving the blows.
The attacker then grabs the woman and throws her to one side and proceeds to kick the victim repeatedly.
The victim was taken to St Vincent’s Hospital for treatment following the incident.
A garda spokesperson said: “Gardaí responded to reports of an assault at Dun Laoghaire train station shortly after midnight on Friday, 12th August 2022.”
“A man, aged in his 20s, was later taken to St Vincent’s Hospital for treatment.”
An investigation into the incident is ongoing.