This paper deals in detail with the concept and the most important characteristics of international organizations as subjects of international law. Aware of the fact that a lot has already been written about this sui generis subject of international law, we will try to contribute to an even better understanding of this complex concept in a study carried out with the method of functional analysis and induction. This will be done by emphasizing the importance of constitutive elements, subjectivity, responsibilities, jurisdiction, and supranationalism of international organizations. We will also propose, as an expression of freedom of scientific thought, some de lege ferenda solutions related to the work of officials in international organizations, all with the aim of further progressive development of international law. In particular, the synthetic and comparative method will support a set of hypotheses and emphasize the supranationalism of international organizations, exemplified by the practice of the EU functioning.