This article uses the concept of institutional sustainability to examine how institutions survive in a context, such as the current one, in which a problematic economy (a decrease of resources), politics (e.g. a crisis of parties and decline in voter participation) and social environment (corruption, wastefulness and administrative malpractice) weaken their legitimacy. Specifically, the purpose of this article is to suggest a conceptual model of institutional sustainability different from the one generally used in the literature on sustainable development to analyse the capacity of institutions to strengthen their roles, tasks and functions with the limited (quantitative and qualitative) resources (e.g. human, economic and instrumental) that they may already have or are given. To this end, the article attempts to 'operationalize' the concept of institutional sustainability, starting with the technical-managerial and political nature of administrative action, and to suggest analytical factors that fall within the sphere of functional autonomy and legitimacy. Points for practitioners This article aims to make the concept of institutional sustainability smoother and more precise by focusing on the intrinsic value of a sustainable way of life for institutions. The specific focus is public administration, now increasingly burdened by the need to combine the political reorganization of public debt with development planning and the provision of services. I suggest some necessary requirements (functional autonomy and legitimacy) to guarantee and/or increase sustainability.