In Donegal, rents were on average 8.5% higher in the first quarter of 2019 than a year previously, according to the latest report from Daft.ie.
The average listed rent is now €645, up 33% from its lowest point.
In the three Ulster counties, rents rose by an average of 9.8% in the year to March 2019 and are now 13% above their previous high in early 2008.
There were just 2,700 homes available to rent nationwide on May 1, the lowest total ever recorded in a series dating back to 2006.
Economist with Trinity College Dublin and author of the Daft.ie report, Ronan Lyons, said that the supply of homes is an issue: “The rental market remains plagued by weak supply at a time of strong demand."
He added that policymakers must maintain their focus on boosting rental supply.