Mathis received his B.A. from University of Bremen and his M.A. from Freie Universität Berlin. From 2012 to 2016, he worked on his doctoral dissertation on international anti-corruption agreements. During his time at BTS, Mathis spent time at Georgetown University (2014) and at UNC Chapel Hill (2015) as visiting researcher. His thesis defense took place in July 2016.

From April 2016 until August 2018, Mathis worked as postdoctoral researcher/ lecturer at University of Greifswald. He has since returned to the Otto Suhr Institute at FU Berlin to work on the DFG-funded research projects "Global Pathways" and "TRANSNORMS". His research is focused on international organizations, norm and policy diffusion, the politics of anti-corruption, and sociology of science applied to International Relations.