Former Minister of Education and Culture from 2000 to 2004, del Castillo was elected to the European Parliament for the first time in 2004. She is a member of the European People’s Party (EPP) and belongs to the Committee on Industry, Research and Energy (ITRE).
She has been, among others, the European Parliament's rapporteur on the European Electronic Communications Code; the Telecoms Single Market Regulation; the Directive on Security of Networks and Information Systems for the ITRE committee; the Regulation on the Body of European Regulators in Electronic Communications' (BEREC); the report on Cloud Computing Strategy for Europe and the Report "A Digital Agenda for Europe: 2015.eu.
She is Co-Chair of the Artificial Intelligence and Digital Intergroup and member of the European Parliament Special Committee on Artificial Intelligence in a Digital Age.
She is the Chair of the European Parliament Delegation for relations with the countries of the Andean Community.
Del Castillo is Vice President of the European Energy Forum and member of the Transatlantic Policy Network and the Board of Knowledge4Innovation (K4I).
Del Castillo is Professor in Political Science and Administration. She obtained a PhD in Law from Universidad Complutense. Before, she had attended Ohio State University on a Fulbright scholarship, graduating with a Master’s degree in Political Science.
She was the Executive President of the Centro de Investigaciones Sociológicas (Sociology Research Centre) from 1996 to 2000.