Calleary has been a member of the Fianna Fáil National Executive since 1997 and has served on party policy committees on Transport, Enterprise and Employment, Agriculture and Youth Affairs.

[3] In 2007, Calleary chaired the first ever Ógra Fianna Fáil branch meeting in Northern Ireland, at Queen's University Belfast.

In February 2008, Calleary was appointed Chairman of Ógra Fianna Fáil, by Taoiseach Bertie Ahern, at the National Youth Conference in Tullamore, County Offaly.

On 22 April 2009, he was appointed Minister of State at the Department of Enterprise, Trade and Employment, with special responsibility for labour affairs.

[16] While Calleary accepted the role, he publicly acknowledged that he was "angry and disappointed" not to have been offered a departmental portfolio and said that he still saw himself eventually leading a department.

[18][19] On 15 July 2020, following the sacking of Barry Cowen from the position, Calleary was appointed as Minister for Agriculture, Food and the Marine by Micheál Martin.

[25] Michael Clifford and Paul Hosford of the Irish Examiner, suggested that the scandal had "left [Calleary's] political career in tatters" and had deeply rocked the Martin Cabinet.