He began his professional career working as a counsel lawyer in the UK and France before entering politics in 1986 becoming a Principal Administrator in the European Parliament.
He served as the spokesman of the Committee on the Affairs of the European Union in both upper and lower legislative chambers.
Martínez-Casan was a member of the Parliamentary Assembly of the Council of Europe as the chairman of the Committee on the Environment, Agriculture and Local and Regional Affairs.
Since 2005, Martínez-Casan has been the director of the European Ideas Network (EIN) a centre-right think tank sponsored by the European People's Party Group (EPP Group).
Since 2009, Mr Martínez-Casan is one of the two co-secretary's generals, with Walid Phares of the Trans-Atlantic Group on Counter Jihad Terrorism (TAG) with offices in Brussels and Washington DC.