Iarnrod Eireann has advised intending passengers to arrive at Heuston Station at least 10 minutes before departure time in the future.
From Monday, a number of services will operate from the new Platform 10, which is across the River Liffey and around one kilometre from the main station.
Passengers travelling to and from Kildare, Cork, Limerick, Galway, Ballina, Waterford, Portlaoise and Tralee will be affected by the changes.