Two out of every five exporters here say they have already been negatively impacted by Brexit, even though the UK has still not left the European Union.
That is according to the results of a survey of over 2,000 clients of Enterprise Ireland (EI), carried out by the organisation.
The research also found that 38% of companies expect their revenue this year to be adversely influenced by Brexit.
Two fifths of firms also expect their profitability to be hit in 2019 by the ongoing uncertainty hanging over the UK's departure from the EU.
A further 29% of companies expect their ability to invest to be negatively impacted, the survey found.
Food exporters appear to have been the worst influenced by the Brexit stalemate, with 60% reporting they had experienced negative impact.
The survey results were released as Enterprise Ireland published details of the export sales recorded by its clients last year.
Brexit has already hit 40% of exporters, says Enterprise Ireland pic.twitter.com/2JpS1C1tIT— RTÉ Business (@RTEbusiness) May 30, 2019
In total, companies assisted by EI sold goods and services worth €23.8 billion outside the state in 2018, a 6% increase on 2017.
Exports to the euro zone grew by 7.6% to €4.8 billion, in line with agency's policy of market diversification ahead of Brexit.
Sales to Germany, France and the Netherlands alone each exceeded €1 billion.
A 5.5% growth in exports to North America was also recorded, rising to €4.08 billion.
Even though there was considerable Brexit uncertainty last year, there was a 4% rise in sales to the UK, which reached €7.9 billion.
The fastest growth sector was construction, where exports rose 22% to €1.97 billion.
"These record export results show the resilience of Irish exporters to grow their global footprint in uncertain times," said Julie Sinnamon, chief executive of Enterprise Ireland.
"Our target is to increase exports to €26 billion per annum by 2020 which we are on track to do. However, a hard Brexit and challenging global trading conditions will negatively impact on export growth for the year ahead," she cautioned.