A new survey shows that nine out of ten Irish hoteliers are concerned about the impact of Brexit on their business next year.
The Irish Hotels Federation has warned that prolonged uncertainty over Britain's withdrawal from the EU could further erode tourism confidence.
The representative body, which carried out the survey, has called on the Government to tackle the high cost of doing business.
Its president Michael Lennon, said: "We are increasingly concerned about the direction that Brexit is taking and the impact that heightened uncertainty is having on our sector.
"A disruptive Brexit would have enormous economic repercussions, which would be felt directly by tourism businesses given our heavy reliance on the UK market."
Ireland is the EU state that would arguably be most affected by a no-deal Brexit.
It has traditionally relied on UK visitors for a significant chunk of its tourism market in Dublin and areas such as the scenic west coast.
Mr Lennon said even if a Brexit deal is eventually reached, any prolonged uncertainty in the coming months could further erode customer confidence.
He added: "The impact would be more pronounced in regions with greater exposure to the UK market, particularly those outside the main tourism hotspots.
"These regions have lagged behind in recent years and can least afford the economic hit."
The hotel industry grew this year but confidence in the future has dropped significantly, according to the IHF.
A fall in UK and Northern Ireland visitor numbers, with sterling weak against the euro, was masked by increases in other markets.
It said nine out of ten hotels were concerned about Brexit and more Government measures were needed to mitigate risks to growth.
The Government has been leading a "Brexit roadshow" for months designed to help businesses around the country to prepare.
Special assistance has been budgeted for in next year's public spending plans and Taoiseach Leo Varadkar has said he does not think an emergency Budget will be needed for a no-deal Brexit.
Some in the tourism industry are smarting from the recent decision to increase the lowered 9% VAT rate to 13.5% after the country recovered from recession.
Mr Lennon said: "The consistent growth achieved over the last seven years in a dynamic and competitive international market cannot be taken for granted.
"We are particularly concerned with the Government's change in approach to tourism and the lack of recognition of the important role it plays as an engine of economic growth and regional balance.
"With the Brexit storm gathering, relentless increases in the cost of doing business, international trade wars, a slowdown in European growth and the increase in tourism VAT, there is little surprise in the drop in business sentiment.
"Many of our members are now re-examining their future investment strategies and taking a more cautious approach to planning for next year and beyond."