This monograph charts and assesses business lobbying in Brussels, taking into consideration its nuances. Indeed, a number of disciplines, theories, and methodological approaches grapple with this subject. The EU is one of the largest trading blocs and lobbying environments in the world. It is also a unique socio-political arena, in constant flux over the last fifty years. Business has not been idle; expanding its reach outside of the national domain, since the 1970s it has developed a spectacular advocacy toolbox, particularly in Europe and the US. Government affairs offices in Brussels today hardly resemble those forty years ago in quality or quantity. The relationship, is multi-layered, multi-level, multi-actor, and cuts across a series of institutional, thematic, legal, social, and governmental networks. With this in mind, this monograph draws on two different disciplines that act as a theoretical prism: political science, and business and management studies. The former helps make sense of the demand side of the equation, the role of government in shaping business activity. The latter provides the supply side, the company’s inner workings and its strategic choice to mobilize and lobby the EU. We employ three analytic perspectives: (i) macro; (ii) meso; (iii) micro. Bringing together different perspectives to business-government affairs in the EU, we aim to provide a rounded theoretical understanding of the relationship, a rich set of conceptual tools for its examination, and a detailed empirical mapping.