A boost to tourism numbers this year is no surprise as the sector was decimated by the volcanic ash cloud in 2010, experts have said.
Official figures revealed almost 1.8 million trips were made to the country between April and June - up 240,000 or 15% on the same period last year.
But tourism chiefs said comparisons with 2010 - when European airspace was closed by Icelandic volcanic ash - were distorted.
Tourism Minister Leo Varadkar said: "While the figures are a positive indication, we cannot afford to be complacent.
"With continuing economic uncertainty in most of our key overseas markets, the tourism agencies and the industry will continue to work together to restore sustainable growth to this vital sector.
"The Government is playing its part through measures such as the VAT cut, reduced employers' PRSI, and the visa waiver scheme, to support competitiveness as well as key investments to upgrade our tourism products and attractions."
The Central Statistics Office figures showed almost three million visitors arrived through Irish airports and ports in the first six months of the year, up from 2.6 million.
Niall Gibbons, chief executive of Tourism Ireland, revealed May was also particularly positive for tourism, with the historic visits of Queen Elizabeth and President Barack Obama and the Uefa Europa League final in Dublin.
"Anecdotal reports from our industry partners around the island of Ireland confirm a more positive picture overall than this time last year," he said.
Visitor numbers from the UK rose by almost 100,000 to 1.3 million up to the end of June, while trips by residents from North America went up to 462,400.