The national average monthly rent is now more than €1,300.
The latest quarterly report from Daft.ie says rents rose 12.4% in the year to the end of June.
It's the ninth consecutive quarter that rents have increased.
In Dublin, the average rent is more than €1,900 - that's one third higher than at the previous peak a decade ago.
Image: Daft.ie
Trinity College economist Ronan Lyons is author of the report, and says other cities are catching up.
He explained: "Two of the cheapest cities - Limerick and Waterford - have seen increases of 20% in the last year.
"That, I think, is evidence that the scarcity has spread all across the country."
He added: "For both Limerick and Waterford, especially, this time of year there would be a lot of student demand for rental accommodation - I think that may have pushed rents up quite a bit."
