The study aimed to substantiate the theoretical foundations of the financial mechanism for ensuring sustainable development of the agricultural sector. The study analysed scientific approaches to the definition of the essence of the financial mechanism in the context of ensuring sustainable development and formulated a new definition as a complex system of financial relations, which is implemented through a set of interrelated elements aimed at achieving balanced economic growth, social justice and environmental safety. The study defined the structure of the financial mechanism, which includes financial methods, levers, instruments, regulatory and information support, and reveals the peculiarities of their application in the agricultural sector, incorporating the specifics. The study established that financial methods form the methodological basis for the functioning of the mechanism, financial levers are the means of implementing the methods, and financial instruments ensure the practical implementation of financial relations. The functions of the financial mechanism (mobilisation, distribution, stimulation, control, stabilisation) were systematised and the specificity in the economic, environmental and social spheres was identified. Based on a comparative analysis of international practices, the study determined that the integration of environmental criteria into Brazil's lending policy reduced greenhouse gas emissions by 10-15% in the agricultural sector, while the Canadian agricultural insurance system reduced the volatility of farm income by 35-40%. The study determined that the Polish Rural Development Programme ensured an increase in the share of organic production from 3.5% to 7.2% in 2015-2020, and in Hungary, more than 12 thousand small farms received access to financing. A system of indicators for assessing the effectiveness of the financial mechanism by three dimensions of sustainability was developed for a comprehensive assessment of performance, incorporating all aspects of sustainable development. The importance of the financial mechanism's adaptability to changing environmental conditions, especially in the context of climate change and market fluctuations, was substantiated. The results obtained can be used to develop strategies and financial programmes for sustainable development of the agricultural sector, incorporating regional specifics
financial instruments; greening of production; green financing; investment instruments; triple bottom line; adaptability