In the last decades the term sustainability has become indispensable for society, governments and companies. Its correct implementation is of utmost importance, and therefore public institutions continuously promote the actions of sustainable development. During the pandemic, universities adapted to online teaching, using different platforms or even social media. The intensity of social media use has had positive and negative impacts. Several studies have linked the use of social media to sustainable development. Therefore, this study analyses the intensity of social media use in public universities and the relationship between the three dimensions of sustainability. To achieve the objectives set out, a sample of 447 users was used, and the data was analysed based on PLS-SEM (Partial Least Squares Structural Equation Modeling). Variance-based SEM is a methodological option to carry out analyses that measure the simultaneous behaviour of dependence relationships. The results have shown that the intensity of the use of social media and the economic sustainability of universities is weak, even if it is positive. Furthermore, there is a strong and positive relationship between the three dimensions of sustainability at the university level. This study contributes to the academic literature on the subject and highlights the critical role of higher education institutions in promoting sustainability.