The purpose of this thesis is to investigate to what extent two important theoretical perspectives - the Uppsala internationalization model and the Born-globals perspective - explain aspects of the internationalization process of an international non-governmental organization (NGO) from the process perspective. To achieve this goal, this thesis made use of a longitudinal single case study method and seeks to fill a theoretical gap, since few studies have been found on the subject. In the literature review section, an analysis of the theoretical perspectives is adopted in order to define the main categories to be applied to the case. Also a review of the concepts associated to NGOs in general and specific studies on internationalization of NGOs are presented. The case studied selected is the NGO called Doctors Without Borders (Médecin Sans Frontières). The selection of this case was made due to the large availability of secondary data, such as reports, books, theses, published interviews, documents, etc. , since it is a large and respected organization. The use of published testimonials was very useful, since it allowed to collect data in greater depth and quality than would be possible using local interviews. The analysis proceeds as following: first, a detailed description of the case history was made in order to provide an overview of the evolution of the NGO over time. Second, the selected categories were analized in order to examine the extent each of it would or would not manifest itself in the case of the NGO studied. At this stage, we sought to detail data and statements to support the interpretation of each category. Overall, there are elements of confluence between the two theoretical perspectives adopted. Nevertheless, as NGOs being a very specific organization, further studies are suggest in order to adapt those perspectives to this specific context in which these kind of organizations operate. The study is limited by the fact that only a single case has been analyse, although in depth, suggesting the continuance of debate in future studies that can contribute to the theorethical development of the internationalization process of these type of organization.