This paper seeks to encourage deeper scientific discussions about the country’s modernisation in the context of social environmental sustainability. Emphasizing the importance of this study, the research problem was identified in response to the questions of how the country’s modernisation manifests itself in the context of social environment sustainability and what are the consequences for the society. This paper is based on a quantitative empirical study to support the structural perspective of the modernisation of the country, to develop an integrated system of indicators for the formation of a modern country following an analysis of the country’s modernisation trends in terms of the social environment. The scientific value of the study: the present paper investigates the ‘soft’ determinants of social environmental sustainability of the country; provides a methodological framework for the methods used (descriptive statistics, confirmatory factor analysis (CFA) and structural equation modelling (SEM). A three-dimensional research approach, covering the education system and educational culture; socio-economic integration; the legal system and the importance of public administration and citizenship, was utilized. A cross-sectional survey of 1021 respondents and structural equation modelling were selected as the main research tools. Lithuania served as an empirical basis for the research. It was revealed that the most important factors in shaping the modernisation of the country through the lens of social environmental sustainability are the participation of citizens in social communities and social activities. Factors that need improvement are public participation and tolerance for the disabled.