30th Dáil Éireann (2007–2011)

In 2007, following his inaugural election to Dáil Éireann, then Taoiseach and Leader of Fianna Fáil Bertie Ahern appointed Byrne as the Government Convenor of the Oireachtas Joint Committee on Social Protection and as a member of the Joint Oireachtas Committees on Justice and Defence, European Affairs and Finance, respectively.^[9]

During this period, Byrne was selected as a Fianna Fáil parliamentary party delegate to the National Forum on Europe.^[10] Following the initial unsuccessful referendum to ratify the Lisbon Treaty, Byrne was appointed to an Oireachtas sub-committee tasked with reviewing the causes of the Lisbon Treaty's rejection by the Irish electorate in June 2008.^[11] The Treaty was subsequently adopted following a second plebiscite in October 2009.

While serving his first Dáil term, the issue of young couple mortgage arrears in Meath East was one of Byrne's primary focuses as he co-authored a bipartisan report which instituted revised code of conduct regulations for mortgage lenders operating in Ireland.^[12]

In June 2009, following selection to run alongside the existing Fianna Fáil MEP Liam Aylward, Byrne unsuccessfully contested the 2009 European Parliament election for the East constituency receiving a total of 33,383 votes.^[13]

In November 2009, Byrne was appointed Uachtaráin (or President) Ógra Fhianna Fáil by then Taoiseach and Leader of Fianna Fáil Brian Cowen at the Ógra Fianna Fáil National Youth Conference.^[14]

24th Seanad Éireann (2011–2016)

Byrne lost his seat in the 2011 general election. He was elected as a Fianna Fáil senator for the Cultural and Educational Panel, and was appointed by then Leader of the Opposition Micheál Martin as Seanad Éireann opposition front bench spokesperson on Public Expenditure & Reform, and subsequently Health.^[15]

In March 2013, Byrne unsuccessfully contested a by-election in Meath East, which was held following the death of former Fine Gael TD Shane McEntee. Although Byrne received 8,002 first preference votes, he lost out to Shane McEntee's daughter, Helen McEntee, who replaced her father as a Meath East TD representing Fine Gael.^[16]

In May 2014, following selection to run alongside the existing Fianna Fáil MEP Pat "the Cope" Gallagher, Byrne unsuccessfully contested the European Parliament election for the Midlands-North-West constituency receiving a total of 64,057 votes.^[17]

32nd Dáil Éireann (2016–2020)

Following the 2016 general election, Byrne was re-elected to Dáil Éireann, receiving a total of 10,818 first preference votes (26.1%).^[18] On returning to Dáil Éireann, Byrne was appointed opposition front bench spokesperson for Education and Skills by then Leader of the Opposition Micheál Martin.^[19]

As opposition spokesperson for Education and Skills, Byrne opposed so-called 'baptism barrier' which was instituted in oversubscribed Irish Catholic primary schools. The practice, in line with Catholic primary schools admissions policies at the time,^[20] involved the lawful discrimination of student registration on the basis of religion. Following a bipartisan initiative to remove the obstacle, led by Byrne and then Minister for Education and Skills Richard Bruton, The Education (Admission to Schools) Bill was enacted by the Oireachtas, which prohibits selective enrolment predicated on religious factors.^[21]

In November 2019, Byrne was appointed Director of Elections by Fianna Fáil leader Micheál Martin for the 2019 Dublin Fingal by-election, to fill the Dáil vacancy created by the election of former Independents 4 Change TD Clare Daly to the European Parliament.^[22] However, Fianna Fáil Senator Lorraine Clifford-Lee lost the election to Green Party candidate Joe O’Brien TD.^[23]

33rd Dáil Éireann (2020–present)

In February 2020, Byrne was re-elected to Dáil Éireann as a TD for Meath East, receiving 6,039 first preference votes.^[24][25] Following the election, as no single party received a governing parliamentary majority, Fianna Fáil leader Micheál Martin assembled a six-person negotiating team, of which Byrne was a member, tasked with reaching out to like-minded political parties with the intent to form a government.^[26] After five months of discussion, held during the COVID-19 pandemic, Fianna Fáil, Fine Gael and the Green Party reached an unprecedented agreement to coalesce and establish a governing majority.^[27] Following the election of the Government of the 33rd Dáil, Byrne was appointed Minister of State for European Affairs by Taoiseach Micheál Martin.^[28]

In May 2020, speaking as opposition spokesperson for Education and Skills, prior to his appointment as Minister of State for European Affairs, Byrne called on the Government, and Minister for Education Joe McHugh TD, to cancel the 2020 Leaving Certificate and implement "fair alternatives" to alleviate undue student stress and anxiety following months of national uncertainty caused by the COVID-19 pandemic.^[29] The call received widespread support and led to the adoption of a predicted grading system in place of the traditional Leaving Certificate for 2020.^[30]

In December 2022, he was appointed as Minister of State at the Department of Tourism, Culture, Arts, Gaeltacht, Sport and Media with special responsibility for Sport and Physical Education following the appointment of Leo Varadkar as Taoiseach.^[31]