His early work was in decorative arts and design, collaborating on the publication "Decorative Model" published by Thienemann Verlag of Stuttgart. His first painting, "Duke Alba at the Castle of Countess Catharina von Schwarzburg", won an award at the 1873 Vienna World's Fair. As a student and, alongside Karl von Piloty, Widnmann was commissioned to decorate the Pringsheim Palace in Berlin. He painted murals for the Munich palace of Prince Leopold of Bavaria and "Homecoming from the Hunt" for the Schloss St Emmeram, of the Prince of Thurn und Taxis in Regensburg.