Services will be altered and, in some cases, bus transfers will be in place.
Irish Rail works on the line between Kildare and Portlaoise continue tonight.
These engineering works will mean alterations or delays to some services tonight, on Thursday and Friday nights.
In some cases, bus transfers are in operation.
The services affected over the next three nights are:
22:10 Heuston to Portlaoise will operate to Kildare only, bus transfers direct from Kildare to Portlaoise, second bus transfer from Kildare to Monasterevin, Portarlington and Portlaoise
20:33 Portlaoise to Heuston will operate in an altered path
21:25 Portlaoise to Heuston is cancelled
22:30 Portlaoise to Heuston will commence from Kildare at 23:05 and will operate in an altered path