Michael O'Kennedy was born in Nenagh County Tipperary in February 1936. he was educated in Ennis, Maynooth, University College Dublin and Kings Inns. He qualified as a barrister. In 1965 he was unsuccessful in his bid to win a Dáil seat for Fianna Fáil. He was, however, appointed to Seanad Éireann. In 1969 he was elected to the Dáil and became Parliamentary Secretary to the Minister for Education the following year. In 1972 he was appointed to the government, however he didn't have a portfolio. In January 1973 he became Minister for Transport and Power.
During Fianna Fáil's period in opposition O'Kennedy revealed his leadership aspirations. He became associated with a hardline policy document regarding Northern Ireland in 1975. The document called for a withdrawl of the British Government from the North. This was against the wishes of the party and was against party policy. In 1977 Fianna Fáil returned to power and O'Kennedy was appointed Minister for Foreign Affairs. In 1979 he publicly supported Charles Haughey's successful leadership bid. He narrowly beat the other contender, George Colley.
In 1981 O'Kennedy became a European Commissioner. He returned to Ireland in 1982 to contest the genaeral election. He demanded a senior government position from Haughey, however, his request was refused. In 1987 he became Minister for Agriculture and Food. In 1992 Albert Reynolds became Taoiseach and O'Kennedy became Minister for Labour. This was seen as a demotion. Worse was to come when he failed to retain his Dáil seat in the 1992 general election. He was then appointed to Seanad Éireann.
O'Kennedy was re-elected in the 1997 general election. That same year he sought the Fianna Fáil nomination for President of Ireland. He only received a mediocre 21 votes out of a total of 112. After the 2002 general election he resigned from national politics.