Transfer pricing (TP) is based on many principles – the essential one is the Arm´s Length Principle (ALP). In this respect, the term “associated persons” is of crucial importance: associated persons must be involved in transactions in order for the ALP to be applied. The aim of the paper is to contribute to existing comparative analysis of TP rules – specifically, to provide a critical analysis of the term “associated persons” as prescribed by domestic law in Brazil, the Czech Republic, and Latvia. The key goals of the research conducted were to provide a comprehensive picture of the variety of definitions, to indicate relationships between international law and domestic law, and last, but not least, to highlight various concepts of the term “associated persons” and to identify problematic aspects connected with the interpretation of the definitions and the applications of the related rules. The study, which is based on qualitative research, is exploratory and interpretative in its nature. Its results present a background for further research and point to the fragmentation of law on TP with respect to the investigated issue.