Karl Wagner was a student of Ludwig Des Coudres at the Art Academy in Karlsruhe from 1854 to 1864 and later moved to Düsseldorf. From 1870, one focus of his work was portraits of King and Kaiser Wilhelm I, of Crown Prince Friedrich III, and Bismarcks.

Also he painted scenes from the Franco-Prussian War, which from 1878, he showed in the Berlin Academy exhibitions. These included depictions of the peace negotiations in Versailles and the encounter with Emperor Napoleon III. with Wilhelm I.