Sustainability is a central topic for an increasing number of companies, as a part of their business strategies. Human sustainability, that is, preserving and improving the quality of human life, in other words, maintaining and advancing human capital, appears as one relevant issue in that context. Humans and human capital are the foremost resources for professional service firms. Their role in the international economic scenario will most likely depend on how they deal with human sustainability and the wellbeing of their people. In this perspective, the paper investigates the antecedents, and organisational implications, of human sustainability in such firms using a structural equation model (SEM) developed on 4,301 questionnaires filled by Italian Chartered Accountants. Findings shed new lights on some implications of human sustainability. Results show that human sustainability has a direct and significative impact on a firm's ability to innovate, fostering creativity and intellectual capital, thus being significant for corporate performance. As a practical implication, firms should accordingly shape their business strategies towards accounting for human sustainability aspects.