Security officers on a Dart service had to call for Garda backup after a crowd of up to 50 youths began a fight on one of the trains after it left Howth station on Thursday.
Irish Rail said the incident led to the train being delayed by 30 minutes as it had to stop at Bayside station, two stops down the line, to await the arrival of a number of squad cars.
However, there were no reports of injuries or arrests as a result of the trouble.
A number of passengers chose to leave the train at Sutton and Bayside stations as the trouble broke out on the 5.45pm southbound service.
A spokeswoman for Irish Rail said: “Three of the Brinks security officers on board called for reinforcements from Howth because there was so many of them. Other people got off the train that weren’t involved.”
There was no further disruption to services.
The Garda said members from Howth station responded to the call but the situation had calmed when they arrived and no further action was required.
Howth is a popular destination for tourists and visitors from other parts of the city in fine weather Antisocial behaviour is not uncommon when large crowds arrive in the village.
