One of the aims of this article is to present a theoretical review and characteristics of two decision-making mechanisms in companies: effectuation and causation. As these mechanisms have not yet had an in-depth presentation in Polish research reports, a comprehensive analysis of their various aspects can be found in this article, in particular with regard to the early internationalisation of firms. The article is based on the newest literature on the topic. Critical views on the concepts of effectuation and causation have been discussed as well. Another aim was more practical: to present the current state of research on effectuation and causation, qualitative and quantitative projects, along with examples of several research instruments. The method used in the article is a critical review of the international literature on the topic, including both theoretical and more practical studies. As a result, the Polish terminology in the area has been clearly defined and all the main elements of effectuation and causation logics have been identified. Moreover, relationships between the two mechanisms and early (as well as late) internationalisation of companies have been discussed. One of the results has been to suggest topics of possible further studies, especially with regard to Polish early internationalising firms. In conclusion, it has been confirmed that there is still broad potential for research on the theoretical aspects of the concepts and their role in the internationalisation of companies.