Andrew Balbirnie and Gareth Delany will join international colleague Paul Stirling in the ECB T20 Blast competition.
Irish skipper Balbirnie will join Glamorgan for their campaign, while Leinster all-rounder Delany is off to Leicestershire.
Balbirnie is very familiar with the Cardiff region having gone to University there, also playing for Cardiff MCCU.
Curtis Campher and Kevin O'Brien are also hoping to clinch county deals, but nothing has yet been agreed for the pair. Discussions are believed to be ongoing with Campher the more likely to become the fourth Irish player to agree terms.
While Paul Stirling's Northants deal had been agreed months ago, there were doubts over other players' participation in the Blast, with Ireland keen to boost the quality and profile of their own T20 competition which gets under way on Thursday.
Balbirnie and Delany will play for Leinster Lightning in their home clash with Munster Reds, while Stirling will feature for defending champions Northern Knights in their opener against NW Warriors at Bready.
It is likely to be the only game for them in the competition with the group stages of the Blast running from August 27th to September 20th, with Finals Day slated for October 3rd.
Irish cricketers in global T20 tournaments (Data compiled by Ger Siggins)
Kevin OBrien: England Nottinghamshire, Gloucestershire, Somerset, Surrey, Leicestershire Bangladesh Rangpur Riders Caribbean Trinidad & Tobago Red Steel New Zealand Northern Districts Canada Edmonton Royals Afghanistan (in UAE) Kandahar Kings Everest PL (Nepal) Kathmandu Kings XI
Niall OBrien England Kent, Northamptonshire, Leicestershire India (ICL) Delhi Jets Bangladesh Khulna Royal Bengals, Rangpur Riders
Paul Stirling England Middlesex Bangladesh Sylhet Royals, Khulna Titans Afghanistan (in UAE) Kandahar Kings, Kerala Kings (T10) Everest PL (Nepal) Chitwan Tigers UAE Delhi Bulls (T10)
Kim Garth Australia Sydney Sixers, Perth Scorchers
Isobel Joyce Australia Hobart Hurricanes