Three of the Taoiseach’s 11 Seanad nominees were selected by Fianna Fáil leader Micheál Martin.
In an agreement reached by Mr Martin and Enda Kenny Fianna Fáil were allowed to make three appointments to the Upper House.
Mr Martin chose the founder of suicide prevention centre Pieta House Joan Freeman, chief executive of Alzheimer's Ireland Colette Kelleher and businessman Pádraig Ó Céidigh.
The Fianna Fáil leader said the three were specialists in areas that required a national focus.
Expressing delight and gratiude over her appointment, Ms Freeman said: “I believe I can make a valuable contribution to the conversation and policy on mental health in particular.
“I’d like to tell all those people who are suffering or are in despair I have your back and I will represent you with every fibre of my being in Seanad Éireann.”
Mr Martin said he did not want to appoint Fianna Fáil members and wanted to take a thematic approach in his nominations.
The deal struck between the two party leaders meant Mr Kenny only had scope to make eight appointments.
The Taoiseach nominated Fine Gael's deputy leader James Reilly to the Seanad.
Mr Reilly, a former minister for children, ran for Fine Gael in Dublin Fingal but failed to get re-elected.
There is strong speculation he will now be appointed Fine Gael leader for the Seanad.
However he will face strong competition from within the party for the position from Jerry Buttimer and Catherine Noone.
Mr Reilly said he did not need any persuasion to sit in the Upper House and he was thrilled to receive the call from Mr Kenny.
The former minister said the Taoiseach would be damned if he did and damned if he did not appoint failed general election candidates.
General election candidates Paudie Coffey, Michelle Mulherin, Ray Butler and John O'Mahony were among the Taoiseach's nominees.
Frank Feighan, who stood aside for the general election in February, was appointed by Mr Kenny.
Mr Coffey ran in the Dáil and Seanad elections but failed to get elected on both occasions.
The last occasion a taoiseach nominated a former TD who did not get elected to both Houses was in 2007 when the then-Fianna Fáil taoiseach Bertie Ahern appointed Ivor Callely.
Mr Coffey’s appointment ensured former leader of the Upper House Maurice Cummins could not be chosen.
The nominations by Mr Kenny mean there is no Fine Gael representative for Tipperary or Longford in either the Dáil or the Seanad.
It had been expected a Senator in Kerry would be chosen but the Taoiseach declined to.
The Taoiseach also reappointed Independent Marie-Louise O'Donnell and chose Billy Lawless who is an advocate for Irish immigrants in the US.
It is widely expected both will largely support the Government on votes in the Upper House.
It is understood the negotiating teams of Fine Gael and Fianna Fail were unaware of the agreement reached by Mr Kenny and Mr Martin.
The Seanad has not sat since the general election three months ago and will now meet on June 8th.
Fine Gael will have 19 votes in the Upper House. Independents will have 14 votes.
Fianna Fáil has 14 votes, Sinn Féin has seven, Labour has five and the Green Party has one.
This means the Government will still not have the balance of power in the Upper House and will require the support of a number of Independents or Fianna Fáil to pass legislation.
The agreement between Mr Kenny and Mr Martin also stretches to the appointment of the Cathaoirleach of the Seanad.
Denis O’Donovan is expected to be given the role and will replace Fine Gael’s Paddy Burke.
The 11 Taoiseach’s nominees are:
1. Paudie Coffey (former minister of state for housing)
2. Joan Freeman (founder of Pieta House)
3. Michelle Mulherin (former Mayo TD)
4. Ray Butler (former Meath West TD)
5. Frank Feighan (former Roscommon-South Leitrim TD)
6. John O'Mahony (former Galway West TD)
7. Dr James Reilly (Former minister for children)
8. Billy Lawless (advocate for Irish immigrants in the US)
9. Colette Kelleher (CEO Alzheimers Ireland)
10. Pádraig Ó Céidigh (chairman of Aer Arann)
11. Marie-Louise O’Donnell (university lecturer and former Senator)