The specific system of governance in different countries, regions, subsectors, etc., eventually determines the speed and type of socio-economic development. Despite its big academic and practical importance, in Bulgaria and other countries in East Europe, there are very few empirical studies on dominating governing structures in agriculture, and their impact(s) on agrarian sustainability. In this paper the interdisciplinary New Institutional Economics framework is incorporated, and the impact of diverse market, private, collective, public and hybrid modes of governance on agrarian sustainability at the current stage of development in Bulgaria assessed. First, the methodological framework of the study is outlined. After that dominating governing modes in Bulgarian farms of different juridical type, size, specialization, ecological and geographical location are identified, and their impacts on agrarian sustainability and its economic, social, and environmental pillars evaluated. In conclusion implications for further research, public policy improvement, and private managerial strategy formation are presented. Agricultural producers of different use quite unlike mixture of effective market, private, collective and hybrid modes for governance of their activities and relations. Individual factors and modes most contributing to improvement of agrarian sustainability at the current stage of development are: manager’s personal convictions and initiatives, farms resources and innovation potential, near future profit and benefits strategies, market prices levels and dynamics, area-based EU subsidies, and informal agreements. Research on relations between the governing structure and agrarian sustainability is to continue though increasing representation, and the spectrum of specific governing modes used by farms of different type as well as assessments of the impact of institutions on agrarian sustainability and the impact of the governance at different hierarchical levels. The latter however, requires a new kind of micro and macro data, and a close cooperation between all interested parties.