Internationalization, or the process of foreign market entry, has lately been a frequent topic of discussion. It is an essential phenomenon that has shaped the economy over the past decades. At a micro level, internationalization can be a very effective tool for supporting sustainable company growth. This paper focuses on the internationalization of Austrian firms in the Czech Republic. It lays down the author´s research into 52 Austrian firms currently present on the Czech market with regard to the eight main internationalization theories and models. Austria plays a very important investment role in the Central and Eastern European region, including the Czech Republic. Indeed, the Czech market is the third largest recipient of direct Austrian foreign investment, following Germany and the United States. After defining the term internationalization, the paper first describes the firms´ entry onto the market, answering the following research questions: How have Austrian firms internationalized on the Czech market and what are their common characteristics? Then, these internationalization approaches are analyzed as follows: the Uppsala model, the network theory of internationalization, the strategic behaviour theory, the international product life cycle theory, the transaction cost theory, the eclectic theory, the behaviourist internationalization theory, and the born global theory. However, their evaluation is only partial and solely based on the research sample. A more complex analysis of the theories and models would require larger samples from different regions and the application of statistical methods.