Export growth from Ireland to the UK fell sharply from 12% in 2015 to just 2% last year.
Total exports to the UK, which account for 35% of net Irish indigenous exports, were worth €7.5 billion last year.
Enterprise Ireland CEO Julie Sinnamon said: “The fact that the growth of exports to the UK has slowed suggests that the impact of Brexit on Irish companies has already started.
Food has been highlighted as a priority sector under the agency’s Eurozone Market Strategy. This strategy aims to grow the value of the country’s second largest export market to over €6 billion in three years.
Sinnamon added: “This strategy is about driving one of the most significant shifts in the footprint of our client exports into the Eurozone.