Introduction. Systemically important banks (SIB) play an important role in stability of the domestic banking and financial system since their activities significantly affect the country’s financial system and the economy as a whole. Problem. Domestic banking system constantly functions in a mode of stress and uncertainty In conditions of war, therefore the National Bank of Ukraine pays special attention to the activities of systemically important institutions. Ensuring the proper functioning of SIB depends on the level of their capitalization, which is why the capitalization of systemically important banks is an extremely urgent issue today. The aim of the article is to determine the ability of SIB to meet capital adequacy requirements as a factor of ensuring the stability and reliability of the domestic banking system and its macroeconomic stress resistance under martial law. Methods. Methods of theoretical generalization, analysis and synthesis, grouping, system approach were used in the paper. Results. The value of the capital standards of domestic SIB during the period of martial law was investigated, a comparative analysis of capitalization indicators of SIB of Ukraine with their normative and forecast values under basic and adverse macroeconomic scenarios was carried out according to the results of the NBU stress testing. Banks that show signs of an unfavorable macroeconomic scenario have been identified, and recommendations have been developed regarding the need to take additional measures to increase the stress resistance of banks. Conclusions. In conditions of war, the SIB of Ukraine fulfills the requirements regarding the target values of the capital standards and has a sufficient margin of safety due to the appropriate level of capitalization, although the implementation of the basic macroeconomic scenario turned out to be impossible, which caused lower than forecast capital indicators. Therefore, the regulator should pay additional attention to those banks that demonstrate negative trends for the implementation of an unfavorable macroeconomic scenario at this stage and prepare a set of measures for their recapitalization in advance.