This study investigates the decision-making logics of entrepreneurs during the exploration and exploitation phases of international opportunities. Data was collected from four med-tech international new ventures in Ireland and Sweden. Adopting a longitudinal approach, we captured the processual dynamics of exploration and exploitation and identified decision-making behaviours adopted by INV entrepreneurs in different phases of the international opportunity process. This study finds that he entrepreneur’s decision-making logic falls contingent on their personal knowledge base and nature of industry dynamics surrounding the exploration and exploitation processes. The study finds that those entrepreneurs with a scientific and engineering background drew on causation decision-making logic in the exploration processes concerning technology development, whereas during the exploitation process they enacted more effectuated behaviours in decisions particulary relating to marketing experimentation and development, mainly due to their lack of prior commercial experience and business know-how. This study contributes to the domain of international entrepreneurship (IE) research with a particular focus on decision-making logic in the exploration and exploitation processes of international opportunities. It offers empirical insights into the degree of applicability of effectuation and causation logic in entrepreneurial decision-making. As IE is a young discipline, this study makes a number of inroads in advancing knowledge in the causation and effectuation theoretical perspectives on IE with specific focus on the complex entrepreneurial processes of exploration and exploitation of international opportunities in high tech contexts.