The number of people employed in companies backed by Enterprise Ireland (EI) rose last year to a record high of more than 215,000.
But the agency has warned that Brexit poses serious challenges for indigenous Irish businesses, particularly those involved in exporting, and those effects had yet to be seen
"However, as the March 29 deadline approaches, and uncertainty continues, we would anticipate that 2019 will be a challenging period for some Irish exporters," said Julie Sinnamon, Enterprise Ireland's chief executive.
"Ongoing doubt about the outcome of the Brexit negotiations, currency volatility, transition arrangements, customs/logistics and potential delays in investment activity are key concerns for exporters," she added.
Ms Sinnamon said that in the event of a hard Brexit, there are in particular 600 Irish companies employing 25,000 staff who would be particularly vulnerable because of their exposure to the UK market.
In total, 18,846 new positions were created in Enterprise Ireland supported firms during 2018, leading the overall number to rise by 4.4%.
However, when jobs lost are taken into account, the net growth in employment at the businesses was 9,118.
The strongest increases were seen in the lifesciences, construction and electronics sectors, mirroring the strength of these areas in the wider economy.
The meat and food sectors also saw solid growth.
Geographically, the new roles were spread across the country, with almost two thirds created outside of the capital.
With huge uncertainty still facing Irish businesses about what form, if any, Brexit will take, Enterprise Ireland says it was involved in a significant amount of work getting firms ready for all eventualities during the last year.
It said €74m in funding was approved for 535 of the most Brexit-exposed companies, while more than 1,000 companies also received Brexit interventions, including one-to-one consultancy engagements for contingency planning, training, and innovation.
"While 85% of our clients have taken Brexit actions, our continuous efforts to support our clients to innovate, diversify and compete will ramp up so that Irish businesses are equipped to mitigate against the fallout of Brexit and build on the strength of the 2018 results," Ms Sinnamon said.
The State agency will also widen its overseas presence during this year in an effort to help Irish firms diversify into new markets by opening 14 new foreign offices in 18 priority markets.
These include France, Germany, Denmark, the US and Australia, while staff numbers in existing overseas offices will also be boosted.
The results have been welcomed by Minister for Business, Enterprise and Innovation, Heather Humphreys, who said they were a great achievement, especially in the context of Brexit.