[4] He became an acquaintance of Lajos Kassák, and published linocut drawings in the modern art magazine MA (Tájkép fával – "Landscape with a Tree", 1917; Kompozíció két alakkal – "Composition with Two Figures", 1919),[5] as well as contributing to the joint exhibits the latter organized, before being showcased in Vienna and establishing connections with Herwarth Walden and his Expressionist group around Der Sturm — eventually, he adopted the style, continuing to be directly influenced by the abstract art of Wassily Kandinsky and Kazimir Malevich, and moving towards a non-figurative outlook.

[7] Present in Budapest at the time of the Aster Revolution, Mattis-Teutsch probably witnessed first hand the establishment of the Hungarian Soviet Republic; despite conflicting accounts and his socialist creed, it seems that he was not involved in the pro-Bolshevik movement.

[2] Active inside the Contimporanul group in Bucharest (with Victor Brauner, M. H. Maxy, and Marcel Janco) and with Das Ziel in Braşov,[8] Mattis-Teutsch was immediately hailed by modernist critics (including Nicolae Tonitza, Otto Bratskoven, Sigmund Maur, Lucian Blaga, Károly Kós, Eugen Jebeleanu, and Ernő Ligeti).

[9] His works were presented at the 1924 international exhibition organized by Contimporanul, alongside those of Kurt Schwitters, Paul Klee, Constantin Brâncuși (whom Mattis-Teutsch had already met in person),[10] Hans Arp, Janco, Brauner, and Maxy.

[13] At the end of World War II, with the onset of the Soviet occupation and, eventually, the establishment of the communist regime, his earlier work was subject to propaganda attacks while he attempted to adapt to the themes of Socialist realism,[2] creating portraits of Joseph Stalin and Stakhanovite scenes featuring bricklayers and miners.