A no-deal Brexit will lead to job losses, lower wages and higher prices in shops, the ESRI has warned.
The institute's latest study, conducted with the Department of Finance, says there'll be a negative impact on the Irish economy no matter how Britain leaves the EU.
However, if they leave with no deal, an estimated 80,000 people could lose their jobs.
The ESRI examines two types of potential no-deal scenarios - one where there's an 'orderly period of adjustment for trade', and a disorderly exit where there's additional disruption to trade in the short-run.
The study finds that GDP in Ireland ten years after Brexit will be around 2.6% lower in a deal scenario, 4.8% lower in a no-deal scenario, and 5.0% lower in a disorderly no-deal scenario.
ESRI Senior Research Officer, Dr Adele Bergin, explained that a disorderly scenario would also be bad for trade and jobs.
She observed: "Unemployment in the long-run in a no-deal scenario would be between 3.2% and 3.4% lower in the long-run compared to where it otherwise would have been, and around 1.8% lower in a deal scenario.
"It'd be a loss of around 40,000 jobs in a deal scenario, and double that in a no-deal scenario."
She added: "In our disorderly scenario in the short-run, the level of output [in the economy] by 2020 could be around 2.4% lower than where it otherwise would have been had the UK stayed in the EU."
The study also suggests that Ireland might benefit from the relocation or diversion of foreign direct investment from the UK - but that positive effect would be outweighed by the negative trade effect.
The findings have been released a day after MPs in the House of Commons voted to take control of the Brexit agenda.
They'll now hold a series of 'indicative votes' on alternative Brexit options - ranging from a softer Brexit to a second referendum - tomorrow.