Rents fell by 2.1% on average last month compared to March, reflecting the economic fallout from the Covid-19 pandemic.
This represents the biggest monthly fall in rents since March 2009.
The average monthly rent nationwide stood at €1,418 in the first quarter of 2020, the figures show.
The latest Rental Report by Daft.ie also shows the number of homes available to rent nationwide on 1 May was almost 40% higher than on the same date a year ago.
The author of the report, Assistant Professor of Economics at Trinity College Ronan Lyons, said a fall in demand for accommodation has impacted rent prices nationally, which the latest Daft.ie report shows.
Speaking on RTÉ's Morning Ireland, he said the figures show the biggest one month fall in rents in over 11 years, since early 2009.
He said that with the broader economy in crisis and many people becoming unemployed this "has fed through to the property market".
He said that the lack of movement of people to take up new roles or education may have impacted the figures.
The report showed an increase in the number of rental listings in central Dublin and central Galway in the second half of March.
There were an extra 500 properties available to rent over the last two months in Dublin.
The Irish Property Owners' Association (IPOA) said landlords and tenants are facing challenging and problematic situations.
"Some Tenants are holding back on their Rent as they cannot afford to pay or in some cases just won't pay and then you have the Tenants who pay as before," said Stephen Faughnan, IPOA Chairman.
"All this is having a big effect on the sector but it is our opinion that this will be short lived."
"We expect the country to commence the return to work and the process of normality returning will increase demand for units and the current supply will be taken up rapidly."