The number of passenger journeys made on DART, Commuter and Intercity rail services in the first three months of 2015 was up almost 4% on the same period last year.
December's price increase has not affected passenger numbers and more than nine million journeys were made in January-March.
That is an increase of 3.8% on the same period last year. The main growth was seen on DART services, which were up 6.1%.
Iarnród Éireann said the general increase in passenger numbers is due to a number of factors, including the Leap Card and online promotions.
The company has also outlined its intention to expand the frequency of services next year.
Plans to increase DART services from every 15 minutes to every ten minutes are under way, with driver training prioritised to meet the additional requirement.
Iarnród Éireann spokesman Barry Kenny outlined the company's plans to expand services next year.
Speaking on RTÉ's Morning Ireland, he said: "We have been adjusting train services so we can continually review that and respond to the demand as it develops.
"And we are also working with the National Transport Authority in terms of looking at service expansions particularly with a look at that DART growth."
Mr Kenny also said that passengers can voice any concerns about the country's rail and DART service when a public consultation will take place this year.
"The network is underfunded at the moment for the service that we are contracted to provide and the [Transport] minister has said there will be a full rail review this year, a public consultation, essentially saying to people what do you want from the rail service strategically going forward, what scale of network is appropriate and how we are going to pay for that".
