The growth of the International Baccalaureate (IB) worldwide is part of a global trend towards the internationalisation of education (IE). Its implementation, nonetheless, takes different forms depending on national and local contexts. This paper examines the recent expansion of the IB in Madrid, drawing upon the sociology of education policy enactments and recontextualisations and the Cultural Political Economy approach. Combining in-depth interviews, document analysis and secondary quantitative data, this paper shows why Madrid has led the expansion of IB schools in Spain in the last decade, an expansion, which has nonetheless remained relatively unnoticed. Our findings suggest that the growth and penetration of private international education initiatives such as the IB may be related to particular social factors, education system characteristics and education policy ensembles, with a particularly intense manifestation in decentralised systems where neoliberal and neoconservative policies foster autonomy, competition, internationalisation and 'excellence.'