We propose the concept of opportunity belief as a means of understanding individuals as the interpreters of their contexts over the internationalization process of a firm. To illustrate the concept, we conducted a microhistorical analysis on one of the largest forest industry MNEs with an internationalization history of more than 150 years. Historical archival data and rich secondary material provided access to the reasonings of individuals over the firm’s internationalization. This allowed depiction of different types of opportunity beliefs as the drivers of internationalization actions within particular historical contexts. We portray opportunity belief as a complementary lens to current internationalization models focusing primarily on firm-level development.