Rents nationwide were an average of 0.2% higher in the third quarter of 2011 than a year previously, according to the latest report published by property website Daft.ie.
This marks the first time since early 2008 that rents rose in year-on-year terms.
The average rent nationwide now stands at €825, which is 25% below the 2007 peak.
In the three months to September, rents actually fell slightly in Cork and Dublin, but are higher than a year previously, particularly in Cork, where rents are up by over 6%.
In Galway, Limerick and Waterford, rents rose slightly in the third quarter, but are 1.5% lower than a year previously.
In commuter-belt counties surrounding Dublin rents are 1% lower, while elsewhere in the country rents were typically static over the summer, but are down 2-3% on the same time last year.
Daft.ie economist Ronan Lyons said rents had now effectively been static for almost two years. But he said there were differences between urban and rural areas, with greatest demand and smallest oversupply in Cork and Dublin in particular.
The Daft.ie report is based on an analysis of 41,000 new properties posted for rent on the site between August and October 2011.