Iarnród Éireann has advised customers that there is serious disruption to southside DART services and Rosslare-Gorey rail services.
The rail line is closed between Grand Canal Dock and Sydney Parade in Dublin due to flood damage at a bridge over the river Dodder near Lansdowne Road.
Dublin Bus will accept rail tickets for customers travelling between the two stations.
The Rosslare-Gorey rail service will run to and from Bray, with a bus transfer between Bray and Connolly Station.
Other commuter services that operate from Drogheda or Maynooth to Dún Laoghaire and Bray will now only operate from Drogheda or Maynooth to Pearse Station.
Iarnrod Eireann spokesman Barry Kenny said remedial work on the bridge would be completed as soon as possible.
Updated service information will be available on www.irishrail.ie and by following @irishrail on Twitter.
