Sian Leathem commenced in the Complaints Commissioner role at the NDIS Quality and Safeguards Commission in January 2022 and has two decades of senior executive experience in both State and Commonwealth agencies across a range of dispute resolution and regulatory areas. Prior to joining the Commission, she was the Registrar and CEO of the Administrative Appeals Tribunal (AAT), which is responsible for conducting independent merits review of administrative decisions made under Commonwealth laws, including a range of decisions relevant to the NDIS.

Sian led the project team responsible for merging 22 existing tribunals into the New South Wales Civil and Administrative Tribunal (NCAT) and performed the role of Principal Registrar of that amalgamated tribunal.

Prior to her role at NCAT, Sian was the Registrar of the Workers Compensation Commission of NSW. She also has a wealth of legal policy experience that she gained through various roles in the NSW Department of Justice and in the Department of Prime Minister and Cabinet.

Sian holds degrees in Arts, Law and Public Administration and is a nationally accredited mediator. She has received an Excellence in Government Legal Service Award from the Law Society of New South Wales and an Excellence in Leadership Award from the NSW Department of Justice. In 2011 Sian was a recipient of the Young Public Sector Leader Award by the Institute of Public Administration Australia.