The aim of this article is to present an approach to assessing the most significant negative factors that have arisen as a result of the introduction of martial law on the decision-making system and the implementation of managerial decisions in the context of ensuring the financial security of a modern enterprise. For this purpose, the object of research is the financial security of machine-building enterprises. A review of the literature has shown that a significant number of scientific papers today aim to present ways to increase the level of financial security, but not all of them understand that the most significant need of the subjects of financial support of machine-building enterprises is the assessment and consideration of negative factors in decision-making. Thus, the scientific task was to present a theoretical and methodological approach to assessing the negative factors of martial law on the management of financial security of a modern Ukrainian enterprise in the field of mechanical engineering. The problem was solved using the methods of system and hierarchical analysis, graph theory and on the basis of expert assessments. As a result, we presented step-by-step instructions on how to assess the negative factors and identified the most significant of them, the consideration of which is critically important in the process of managing the financial security of a modern Ukrainian machine-building enterprise. Prospects for further research will be based on expanding this list and narrowing the focus on the internal processes of machine-building enterprises.