Michael McGrath will be Ireland's nominee for the European Commission with Jack Chambers set to take over as finance minister.
The nomination of Mr McGrath by Fianna Fáil leader Micheál Martin was discussed at meeting of the three Government coalition leaders on Monday evening.
Mr McGrath will succeed Fine Gael-nominated commissioner Mairead McGuinness.
Simon Harris said that Mr McGrath was "a nominee for Ireland". He said that Mr McGrath had been "trained by the people of Carrigaline and his standards are of the highest level".
Speaking before the Cabinet meeting on Tuesday, Mr Harris said: “I’m conscious that when somebody becomes nominated as a European Commissioner, there’s a lot of work to go through in terms of parliament hearings and the like.
Mr Martin said Mr McGrath had steered the Irish economy and "made a large contribution to Ireland" in his four years as a minister. He said Ireland was nominating someone of a "very, very high calibre".
The Tánaiste said Mr McGrath's replacement, Mr Chambers, is "very able, intelligent" and will be a "very effective minister".
Mr McGrath said that it was "an incredible honour" to be nominated and he was delighted to accept the nomination. He said he is "immensely excited" to have the chance to shape policy at a European level. He thanked the people of Cork South Central for their support, adding that he could not have done this without the support of his family, particularly his wife Sarah.
Green Party leader Eamon Ryan said that Mr McGrath was "one of our best" and said that Mr McGrath would be committed to the Green New Deal.
“In my view, it would be prudent to fill that vacancy immediately and I expect any vacancy that may or may not arise today at Cabinet to be filled today.”
Asked if he was aware who would replace Mr McGrath, Mr Harris said: “I am aware of all aspects of what will happen today.”