Judicial legitimacy is fundamental to ensuring public acceptance of courts’ decisions when judges have no electoral mandate. Yet, in Australia, we know very little about the legitimacy of the courts in the eyes of the general public or the factors associated with judicial legitimacy. Drawing on a survey of a representative sample of Australian adults, we address the question: What is the level of legitimacy of, or diffuse support for, the High Court of Australia among the Australian public and what factors are correlated with the legitimacy of the Court? Our findings suggest that judicial legitimacy in Australia is mainly dependent upon people’s commitment to structural democracy and democratic institutions. Consistent with previous studies for the United States Supreme Court, we find that Australians’ loyalty to the High Court is not dependent on ideological commitment, for example, to ideas of tolerance or individual liberty. Instead, diffuse support for the High Court is based, primarily, on people’s level of confidence in national institutions more broadly, on their level of support for notions of the rule of law and on their commitment to the multi-party political system.