Official figures show that the number of visits to Ireland in June dropped by more than 15% compared with the same month last year.
The Central Statistics Office said there were 636,600 trips to Ireland in the month, compared with just below 750,000 a year earlier.
There were big drops in two of the main markets, with visits from Britain down almost 20% to 260,700 and trips from the rest of Europe falling 12% to 219,600.
The figure from North America showed a fall of almost 8% to 121,900.
For the first six months of the year, visits to Ireland are down 10.7% to just over 3.3m.
Irish people made 709,900 trips abroad in June, down 7.6% from the same month last year.
For the first half of the year, there was a fall of almost 10% to just over 3.4m trips.
Meanwhile, Tánaiste Mary Coughlan has said the Government is considering an investment scheme to help those working in the tourism sector.
Minister Coughlan said the tourism sector was 'particularly vulnerable' at this time and companies had expressed the view that they wished to participate in the Employment Subsidy Scheme.
Minister Coughlan said she was working with Minister for Arts, Sports and Tourism Martin Cullen in order to take a 'whole of Government' approach to the tourism sector.
