The new Iarnród Éireann Mark 4 trains, the focus of unofficial industrial action that left thousands of commuters stranded last week, began operating yesterday.
The first of the new Spanish trains made its maiden journey from Heuston Station, Dublin, at 9am, arriving at Kent Station, Cork, at 11.50am.
Attempts by the company to introduce the trains last week lead to a two-day strike.
The trains are part of a €117 million upgrade of services on the Dublin-Cork line.
They have the same capacity as the old trains, but will be run more frequently.
Iarnród Éireann has promised an hourly service from Dublin to Cork by December.
A company spokesman said: "These trains meet all the modern standards of quality and comfort. The seats are more comfortable, there is improved access for the mobility impaired and the toilets are fully accessible."
