Karl Haffner went to the Collegium Fridericianum in Königsberg. Already at 16 years old, he followed a touring company and ran through Prussia as an itinerant play-actor, Saxony, Silesia, Austria and Hungary. After ten years and some dramatic attempts, he became dramatists and theatrical writer at the Pest Theater for Feodor Grimm.

In Pest he wrote tragedies like Die Raubschützen, Die Locke des Enthaupteten, Blocks Totengruft, Schwarzenberg and Palffy und Batorys Tod, which met with the stormy approval of the audience. Oddly enough, in Vienna the known theatrical manager Carl Carl recognised in this Heffner’s talent for the local farce and engaged him for nine years in the Theater an der Wien as a theatrical writer. Haffner had to commit itself to the delivery of eleven pieces in the year. Later he turned to the theatre in the Josefstadt and edited at last the satirical weekly paper Böse Zungen.

Apart from dramas, Haffner wrote also more than 30 volumes of novels. One of it, Scholz und Nestroy (from 1864 to 1866, 3 volumes), contains a miscellaneous selection of stories of his life.

Together with Richard Genée he wrote the libretto for the operetta Die Fledermaus, with music of Johann Strauß.

He was buried on the Wiener Zentralfriedhof in an honoris causa dedicated grave. In the year 1955 a street, the Haffnergasse, was named after him in Vienna Danube district (22nd district).