This paper analyses protection of the principle of child's best interest within the institution of adoption with international characteristics. It defines the institution of international adoption and its historic development. Furthermore, the aim of the next two chapters of the paper is to define the principle of child's best interest and to offer the analyses of the componets of the principle of child's best interest within the framework of international adoption. Subsequently it deals with the principle of child's best interest and its protection within the most relevant international sources that govern the institution of international adoption and Croatian legal regulation of this institution and principle. It demonstrates violation of the principle of child's best interest which can occur because of misuse of the institution of international adoption, with the focus on wartime occupation, natural disasters and children trafficking. The end of the paper deals with two court verdicts which protect child's best interest in international adoption, while the conclusion sets out advantages and disadvantages of the current international and Croatian legal regulations and the ideas for improvement and better protection of child's best interest wihtin the international adoption.