Abstract Philanthropic foundations are key players in global sustainability governance. This paper explores the legitimation strategies these foundations use to justify their actions and positions in the sustainable development community. By combining Theo van Leeuwen’s legitimation framework with our novel analytical justice framework, we offer a new tool to analyse hard-to-research actors. Analysing data from 41 foundation websites, we find that foundations emphasize Global Egalitarian Cosmopolitanism in their values and objectives to align with global sustainability discourses. However, Libertarian ideas dominate when discussing programs and founders. This indicates there may be internal conflicts within foundations over the relationship between extreme wealth accumulation required for global philanthropy and sustainability objectives. In turn, this has implications for how foundations position themselves as agents of justice in sustainable development. While discourse analysis provides valuable insights into philanthropic legitimation strategies, further research is needed to fully understand how justice intersects with organizational decision-making.