The crisis in the domestic economy has significantly worsened the economic situation in the regions. High dependence on federal budget revenues makes it necessary to search for additional sources of funding, that is, to attract investment. The paper analyzes the importance of investment potential in the system of economic stability of the region, presents the system of indicators that reflects the key factors of the social and economic development of the region which influence the interest of the business community in the implementation of investment projects in the territorial entity of the Russian Federation. The threshold values of the indicators are specified, which make it possible to assess the influence of each indicator on the level of investment potential and group them to distinguish the areas of social and economic development of the region that require special attention. The author illustrated the diagnostics of investment potential in the system of economic stability of the region through the example of the Mari El Republic. The study revealed that the region does not meet the necessary threshold values for most indicators, which negatively affects its investment potential and might cause threats to economic stability. The diagnostic results indicate some problems in the economy of the region, such as an extremely low level of innovations in production, a high degree of fixed assets depreciation, a large proportion of unprofitable enterprises, and negative trends in demography which lead to a shortage of labor resources.