This study aims to develop a hierarchical composite indicator using a model-based approach to measure social sustainability in Italy. The proposed indicator is built by integrating manifest variables, including education, quality of life, social relationships, and participation in cultural activities, while examining specific and broader latent dimensions they reflect or form. The hierarchical structure of the social sustainability composite indicator is derived using the Hierarchical Disjoint Principal Component Analysis. Ultimately, this methodology identifies intermediate latent concepts between the manifest variables and the general concept, offering meaningful insights for comprehensively understanding the phenomenon under study, and also allows for testing the nature of the relationships between two sequential levels of the hierarchy. Comparisons across the Italian regions, years (pre- and post-COVID), and genders are provided, enhancing the understanding of social dynamics affecting sustainability in a context marked by significant regional diversity.