Australia was one of the first countries to introduce a mechanism for the ‘screening’ or approval of inward foreign investment, in the 1970s. The mechanism has evolved over time, most recently since the COVID-19 pandemic began in 2020. It purports to reflect Australia’s welcoming of inward foreign investment — consistent with a longstanding commitment to an open economy — while retaining controls to restrict investment. Australia has in recent years expanded foreign investment screening to encompass a broader range of security-related matters as well as the potential for ‘retrospective’ review of existing investments on national security grounds. These security-specific developments build on the general ‘national interest’ test that continues to apply in most cases, which incorporates national security as only one of a range of factors considered. Although Australia’s regime is elaborated in detail in legislation and regulations, some important aspects, including the meaning of national security and the national interest, are explained only in policy documents rather than in law. This aspect of the Australian system increases the discretion of the Treasurer in making relevant decisions, as does the limited transparency of decision-making, regarding not only public notices but also non-disclosure of certain information to the investor applicant.