With rapid globalization, firm internationalization has become an important corporate strategy as well as the necessity for the survival and growth of the business. In the last decade, there has been a growth in literature that studies this field, especially in emerging countries. However, there exists a gap in the literature in CEE countries. This study aims to fill that gap by conducting an analysis and providing insight regarding the factors that lead to an increase in firm internationalization in this region. This research paper studies the main determinants that have an impact on the firm internationalization of large companies in CEE countries using panel data empirical methods, such as the random effect model and generalized method of moments (GMM) model for a panel of 50 firms from 11 CEE countries and a time duration of 14 years. This study determines the main factors that positively influence firm internationalization in selected countries. These countries have experienced a radical transition from centrally planned economies to market economies, and although they have experienced economic growth and a rise in productivity, they are still facing several challenges. Therefore, it is important to know what facilitates and helps firms to expand in international markets. The main findings derived from this study show that firm characteristics, such as age, size and corporate performance, have a positive effect on the internationalization process. An increase in age, size and firm performance leads to higher levels of internationalization. Larger and relatively older firms have access to more resources and are more experienced in dealing with the environmental difficulties characteristic of these countries.