Fiedler sang a wide repertoire that encompassed German, Italian, French, Czech, and Russian opera. Some of the stage roles for which he achieved considerable success are Count Almaviva in Wolfgang Amadeus Mozart's "Le nozze di Figaro", the title role in Pyotr Tchaikovsky "Eugene Onegin", Rodrigo in Giuseppe Verdi's "Don Carlos", Iago in Verdi's "Otello", Scarpia in Giacomo Puccini's "Tosca", Sixtus Beckmesser in Richard Wagner's "Die Meistersinger von Nürnberg", the title role in the "Boris Godunov" and the Jochanaan in Richard Strauss's "Salome".