Aim. The presented study aims to develop a methodological approach to assessing the institutional environment for innovation processes in meso-economic entities using a composite index.Tasks. The author comparatively analyzes methodological approaches to assessing the institutional environment for economic and innovation processes in Russia and other countries, identifies their advantages and limitations; determines institutional factors affecting the state of innovation processes in meso-economic entities; develops the structure of the index for assessing the institutional environment for the innovative development of meso-economic entities; substantiates the composition of sub-indices, the integration of which would make it possible to objectively assess the effectiveness of institutions regulating innovation processes.Methods. The author uses the index method of factor analysis, which makes it possible to incorporate the indicators of the state of institutions regulating innovative processes in mesoentities into the composite index. These indicators reflect the effectiveness of national institutions, the institutional impact of social reforms, and the institutional effectiveness of human capital development. The peculiarity of the proposed methodology is that, when calculating the index, indicative indicators of the effectiveness of the institutional environment are brought to a comparable form through percentage normalization relative to the threshold value of the indicator, leading to their further integration with allowance for the equal value of the weighting coefficients of all indicators.Results. The proposed methodology for calculating the composite indicator of the state of the institutional environment for innovation processes is based on the use of official government statistics, which ensures the verifiability and reliability of the obtained results and the possibility of using them in the compilation of ratings of Russian regions by the level of socio-economic and innovative development.Conclusions. The proposed methodology is an elaboration of theoretical ideas about the institutional environment. This methodology complements the analytical tools for its assessment, which can serve as a basis for the development of new and adjustment of the existing measures for regulating innovation processes in the Russian regions.