[2] On 14 March 1876 Isidor Mautner married Eugenie (Jenny) Neumann,[3] daughter of a wealthy Viennese silk merchant.
[4] With the help of her dowry, a mechanical weaving mill set up in 1868 by the Perutz brothers from Prague was purchased in Schumburg (Šumburk nad Desnou) in northern Bohemia in the same year.
[5] In 1878, he founded the "Baumwoll- und Leinenlieferungs-Gesellschaft für die k. k. Landwehr von Mautner & Consorten" with branches in Prague, Budapest and Trieste as well as a "Konfektionsanstalt" in Vienna.
In order to become independent of supplies "from enemy countries," the Sandau ironworks for the production of weaving machines was also founded in 1916 and a carded yarn and vigogn spinning mill in Friedland (Frydlant) in northern Bohemia was taken over.
"[9][10] Since the Entente powers' naval blockade had brought cotton imports to a virtual standstill, Isidor Mautner switched the production of his mills to paper textiles.
Towards the end of the war, Isidor Mautner headed one of the largest textile groups on the European continent with 42 factories and about 23,000 employees.
In addition, the "Neue Wiener Bankgesellschaft AG," founded in 1921 and managed by his son Stephan, to which he had entrusted his assets, ran into difficulties in 1924.
In an attempt o save the company, Isidor Mautner pledged his real estate holdings to the National Bank, but this failed.
He was a friend of the Burgschauspieler Josef Kainz, played a major role in financing the Theater in der Josefstadt, newly opened by Max Reinhardt in 1924, and was president of the "Wiener Schauspielhaus AG" from 1924 to 1928.