The United Nations Subcommittee on the Prevention of Torture visits signatory nations to the Optional Protocol to the Convention against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment (OPCAT). Its role is to monitor and support signatory nations in implementing and complying with the Convention against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment (CAT). In October 2022, the United Nations Subcommittee on the Prevention of Torture visited Australia but was barred from visiting mental health wards in Queensland and all detention facilities in New South Wales leading to the termination of its visit. This breach of Australia’s obligations under the OPCAT presents a significant setback for the rights of people with mental illness and other involuntarily detained populations. This piece sets out to demonstrate the relevance of OPCAT to the mental health system in Australia. Individuals who are detained for compulsory treatment in locked facilities such as acute psychiatric inpatient wards and forensic mental health facilities are deprived of their liberty, often out of public view. Thus, it highlights the ethical and professional obligations of all mental health professionals, especially psychiatrists, to safeguard the human rights of individuals being detained in mental health facilities as enshrined in Australia’s international legal obligations under the OPCAT. Adhering to these obligations diminishes the risk of future human rights violations of people with mental illness.