	Glennon first held political office when he was elected to Seanad Éireann in a by-election. He remained there until 2002 when he was elected to Dáil Éireann at the 2002 general election. Glennon was Vice-chairman of the Oireachtas Committee on Arts, Sport, Tourism, Community, Rural and Gaeltacht Affairs from 2002 to 2007. He was also a member of the Oireachtas Transport Committee and of the Oireachtas Committee on Procedures and Privileges. Glennon chaired a session of the Dublin Forum – a Fianna Fáil project to allow Dublin residents discuss issues of political significance. He was part of the TV3 Rugby World Cup coverage in 2007.