Seán MacEntee was born in Belfast in 1889. He was educated at St Malachy's and Belfast Municipal College of Technology. He qualified as an electrical engineer. He became a member of the Irish Volunteers and took part in the Easter Rising in 1916. He was imprisoned but was released in 1917.
MacEntee contested the 1918 general election as a Sinn Féin candidate. He successfully became MP for Monaghan. MacEntee took the anti-Treaty side during the Irish Civil War. He was imprisoned by the Irish Free State government. In 1926 he became a founder-member of Fianna Fáil. In 1927 he became a TD for a Dublin constituency, a position he held until 1969. In 1932 MacEntee became Minister for Finance in the first Fianna Fáil government. He also served as Minister for Local Government, for Industry and Commerce, and for Health. He became Tánaiste under Sean Lemass in 1959.
Seán MacEntee died in Dublin on 10 January 1984. MacEntee's daughter is the Irish poet Máire Mhac an tSaoi.