A quarter of public transport users could face fare increases from the beginning of next month.
Some will see increases of up to 18% on journeys.
But the National Transport Authority, which decides fares, says 75% of those who use public transport will see fares stay the same or fare reductions.
Commuters on Dublin Bus, Iarnród Éireann, Bus Éireann and Luas will be affected.
Operators are permitted to implement these fare changes from 1 December.
The NTA says the increase in revenue yield to providers will be less than 1% in 2017.
It says that the Leap Card, which is now used to pay for about 3.5 million public transport journeys in Ireland every week, will still be at least 20% cheaper than cash for a single journey.
Iarnród Éireann Commuters from Sallins/Naas and Kilkock will see reductions on fares of up to 47%.
The stations are being brought into the Dublin Short Hop Zone as part of the new pricing structures.
The NTA says an adult single journey from Heuston Station to Sallins/Naas Station, which currently costs €8.70, will cost €4.60 cash or €3.56 on Leap Card.
