Hackl appeared on numerous stages, in film and TV productions, and was a crowd favourite at Vienna's Burgtheater. In 2012, he was awarded the Nestroy Theatre Prize for his life's work.
Hackl, who turned 65 on May 16, started his career in 1972/73 at the Viennese theatre Die Courage. In 1978, he was made an ensemble member of the Burgtheater.
Some of his most memorable performances included the leading character in Ferenc Molnar's Liliom or Johann Nestroy's Der Zerrissene, as well as various Arthur Schnitzler characters.
At the Volkstheater, Hackl acted and sang Zaza in La cage aux folles and Don Quijote in The Man of La Mancha, among other musical performances.
He also appeared at the world-famous Salzburg Festival.
The actor's work included directing, writing – a book about his long illness and his life on the stage – cabaret, and teaching. Since 1996, Hackl was a professor at the Max Reinhardt Seminar, the prestigious School of Drama at the University of Music and Performing Arts in Vienna.