Landlords will be able to claim tax relief on interest paid on loans used to buy, improve or repair their properties.
The tax relief was due to be 100pc by 2021, but the Government has brought it forward so it becomes effective from January 1 next.
The move will cost €18m in a full year and is aimed at smaller landlords. Between 70pc and 80pc of landlords renting out properties own one or two units each, and the measure is designed to make it more attractive for them to remain in the market.
Housing Minister Eoghan Murphy said the relief was seen as a fair way to keep landlords in the sector, and formed part of a wider reform of the rental sector.
This included additional funding for the Residential Tenancies Board, enforcement of rent pressure zone legislation, and doubling the notice period for renters where a notice to quit was served after six months.
"We're not going to let ideology get in the way of solutions," he said. "We have to make sure there's an incentive for landlords to remain in the market. This was seen as the fairest way for small accidental landlords to get relief on mortgages."
IPAV, the Institute of Professional Auctioneers & Valuers, welcomed the move with chief executive Pat Davitt saying high taxes were among the primary reasons why private landlords were leaving the market.
"Private landlords are treated substantially less favourably by the State than commercial landlords," he said.
"Today's announcement is welcome in this regard, although more is needed."