Born in Dublin, he grew up in Drumshanbo, County Leitrim. He is married to Sheila Baldrey and has five children (2 daughters and 3 sons). His father Joe Mooney was a member of the Seanad (1961–65) and Leitrim County Council (1943–88) while his mother Eva Mooney also served as a member of Leitrim County Council (1988–91). He is the third generation of his family to contribute to public service locally and nationally as his grandfather Andrew Mooney served as a member of Leitrim County Council from 1920–1943.
Mooney has also enjoyed a broadcasting career with RTÉ, Ireland's national broadcaster. A presenter of a variety of Irish traditional and country music and Sports programmes, he has also devised, scripted and presented numerous music documentaries on Irish and American country music stars. In September 2007, he was the recipient of the UK based Irish Post Newspaper Readers Award for 'Services to the Irish Community in Britain' and as a Senator was a leading campaigner for the undocumented Irish in the USA as well as being the 'Voice of the Irish Diaspora' in Seanad Éireann. He presented music programmes on Ocean FM and Dublin's Country Mix 106.8 and completed a series for RTÉ Radio 1 titled 'Irish Music Legends' which was transmitted in August 2008. He also presented a series titled The Irish Abroad and The Irish Experience both programmes dealing with the Irish Diaspora.
He was first elected to the Seanad in 1987, on the Cultural and Educational Panel as a nominee of the Library Association of Ireland (LAI). He retained his seat at each subsequent election until losing it in the 2007 election. He was a member of Leitrim County Council from 1991–1999.
Mooney also served as a delegate to the Parliamentary Assembly of the Western European Union 1998 to 2002 and subsequently was a member of the Irish Delegation to the Parliamentary Assembly of the Council of Europe 2002–08. He was appointed a member of the British–Irish Parliamentary Assembly (BIPA) in 1997 and served until 2007. Mooney returned to the BIPA in 2011 and also sits on the North/South Parliamentary Body which meets twice yearly in Belfast and Dublin and is the representative of the Stormont Assembly and Oireachtas.
In April 2008, Mooney was nominated to the position of Chairman of Fáilte Ireland North West, one of five Regional Tourism Boards in Ireland charged with promoting their regions and attracting tourists.
On 19 January 2010 Mooney was elected on the first count in a Seanad by-election caused by the death of Senator Peter Callanan in October 2009. As a result he took a seat on the Agricultural panel in the 23rd Seanad returning after an absence of two and a half years. He was re-elected at the 2011 Seanad election. He is the Fianna Fáil Seanad spokesperson on Social Protection. He is also a member of the Joint Oireachtas Committee on Agricultural and the Joint Committee on Transport, Energy and Communications.