The thesis addresses the role of national oil companies and their overseas engagement in the foreign policy decision-making process of states. Over the past 40 years, national oil companies have gained importance in the international oil industry and currently control around 90 per cent of the global oil reserves. A number of political and economic factors – depleting domestic reserves, economic growth – have resulted in an increasing expansion of Asian national oil companies to Africa. Through the use of two Asian national oil companies – Malaysia's Petronas and India's Oil and Natural Gas Corporation (ONGC) – and their overseas engagement in Sudan and South Sudan as case studies, the thesis assesses three aspects: factors and motives that influence the relationship between government institutions and Petronas and ONGC, the connection between this domestic relationship and the overseas engagement of both companies, and the implications of the overseas engagement of Petronas and ONGC in both Sudans for the foreign policy decision-making process of Malaysia and India. This set of questions is analysed through a comparative case study design that is supported by in-depth interviews and based on Foreign Policy Analysis (FPA), proposing a four-level theoretical framework. This thesis thus seeks to demonstrate how FPA can help assess the connection between the domestic decision-making process and the international engagement of the companies. In doing so, it not only argues that process and engagement are in fact connected, but also critically addresses conventional assumptions about the overseas engagement of national oil companies. Furthermore, this thesis questions the idea that government institutions and national oil companies act in a coherent and coordinated manner when operating abroad.