This article is devoted to the study of humanitarian action of the international and national actors in Ukraine. The urgency of the work is driven by the deepening of the humanitarian crisis against the background of the continuation of the active phase of the Russia-Ukraine war. The purpose of the article is to generalize the contextual changes of humanitarian action in Ukraine, including institutional, sectoral, managerial and other aspects. The novelty of the study consists in the formulation of proposals for the activation of humanitarian action in Ukraine at the national and local levels, which are rethought through the prism of the international humanitarian system and the features of humanitarian response in Ukraine. The desk research of open sources which is supported by a review of the latest thematic publications, operational summaries, data sets and their analysis is used for this purpose. An overview of the modern international humanitarian system, the main tools and mechanisms of humanitarian response is provided. International and domestic categorical apparatuses in the field of humanitarian action are compared. New dimensions of the humanitarian crisis, systemic challenges and operational problems of humanitarian response that arose after February 24, 2022 in Ukraine are summarized. The funding for humanitarian needs of Ukraine over the past decade has been analyzed, including interagency response plans for Ukraine for 2022 (the Flash Appeal and the Regional Refugee Response Plan). The humanitarian response at the international and national levels has been studied. It has been concluded that humanitarian action in Ukraine is based on reliable tools, mechanisms and models of the international humanitarian system, as well as on its own humanitarian traditions and initiatives. Together, they ensure the effectiveness and efficiency of humanitarian response and contribute to unprecedented financial support for Ukraine in the global dimension. Thanks to this, in a fairly short time, a new space for humanitarian action began to form in Ukraine, in which the presence of international and national humanitarian actors was expanded and the interaction of humanitarian actors was improved.