After studying law at the University of Salzburg, Matthias Neumayr started his judicial training. From 1 February 1984, he worked as a judge at various courts in the province of Salzburg and at the Court of Appeal in Linz. On 1 January 2001, the Federal President appointed Neumayr judge at the Austrian Supreme Court of Justice and, on 1 November 2018, Vice-President of the Court. In the last three decades, he has been strongly involved in judicial training and further education, both in Austria and abroad, for example in Germany, in the Western Balkans (2005–2011) and in Azerbaijan (2007). Since 1 March 2013, Neumayr has also been a part-time university professor for procedural law and comparative litigation at the University of Salzburg.

Between 2016–2017, he was a member of the working group of the ELI ‘Empowering European Families’ project. Neumayr is am currently involved in several ELI projects as an Assessor (The Concept and Role of Courts in Family and Succession Matters; Digitalisation of Civil Justice Systems in Europe) and as a Country Reporter (Project on Model Laws and Supporting Materials for Advance Choices for Future Disablement). He also serves on the ELI Membership Committee and is an author of numerous publications.