The article analyzes the normative consolidation of the principle of the best interests of the child in international acts and legislation of Ukraine. Emphasis is placed on the application of the principle of the best interests of man in the practice of the ECtHR, it is clarified how the case law has influenced the decisions of Ukrainian courts. The categories of cases in which the ECtHR applies the principle of the best interests of the child are highlighted. The peculiarities of the application of the principle of the best interests of the child during the war between Russia and Ukraine have been studied. It is proved that martial law is not a reason to limit the principle of the best interests of the child.