Bus Éireann was the only operator to record a drop in numbers, following three weeks of industrial action
16 million more journeys were made on public transport last year than in 2016, representing an increase of 7%.
New figures show 251 million people used Bus Éireann, Dublin Bus, Irish Rail and Luas services in 2017.
Bus Éireann was the only operator to record a drop in passenger numbers. The decrease from 32.1 million to 31.2 million passengers has been blamed on the industrial action that lasted three weeks.
The biggest percent increase was on the Luas, with a 10.26% jump in passenger numbers - and the National Transport Authority is predicting further 'substantial' growth in 2018 as a result of the newly-opened Green Line extension.
CEO of the National Transport Authority, Anne Graham, suggested an improving economy is among the key factors driving the increase in use of public transport.
She observed: "There's more people in employment, more people shopping and going into town for retail & leisure purposes. We're delighted that more people are using public transport to access those facilities."
She outlined some of the plans for 2018, explaining: "We want to increase the capacity on both Dublin Bus and Bus Éireann services. Iarnród Éireann will be introducing a ten-minute frequency on DART services [and] additional off-peak services on the Maynooth line.
"[That's] along with bus services between Naas and Blanchardstown, and a new Kilkenny city bus service."
Seven new trams are also set to be introduced on the Luas Green Line between January and March, which the NTA says will add more than 2,500 person capacity to the line.