This study investigates the international opportunity exploration and exploitation processes of high technology international new ventures (INVs) operating in the global medical devices sector. Drawing upon the effectuation and causation perspectives, we contribute to the micro-foundations of international entrepreneurship research in the early innovation development space by focusing on decision-making logics of techno-entrepreneurs of INVs. Specific focus is afforded to the phases of their exploration and exploitation of international opportunities leading to international new venture creation. In the pre-start-up and start-up stages of international new ventures, we find that sequential ambidexterity applies to how the subject firms manage the exploration and exploitation of opportunities in the delivery of their innovations to global markets. This research advances prior international entrepreneurship studies by focusing on the opportunity and innovation processes on the individual level. We identify different decision-making logics in the different phases and contrary to earlier findings in the international entrepreneurship (IE) area, we found causation logic to dominate the initial stages of exploration and effectuation logic, in the latter stages. Prior commercial experience presented itself as a key determining factor in the decision-making path chosen by international techno-entrepreneurs. Our study further extends the view of organizational ambidexterity by offering empirical insights into the relevance of sequential ambidexterity for understanding the processes of innovation exploration and exploitation in high-tech INVs and the decision-making logics driving these processes. © 2019 Elsevier Ltd