Manfred Hemm was born in Austria, studied in Vienna and made his debut singing Figaro in "Le Nozze di Figaro". After a triumphant success at the Opera House in Graz as Leporello in the production of Austrian filmmaker Axel Corti, Claudio Abbado and Claus Helmut Drese invited him to the Vienna State Opera and Jean-Pierre Ponnelle engaged him in Venice and Zurich. Herbert von Karajan also invited him to the Salzburg Festival where he performed Figaro (Levine/Ponnelle), Angelotti in Tosca (Karajan), and later roles in Elektra (Abbado) and Die Frau ohne Schatten (Sir Georg Solti). His time in Salzburg led directly to his famous interpretation of Papageno at the Metropolitan Opera in New York with James Levine which he repeated in five successive seasons with enormous success. Manfred became increasingly well-known for his Mozart roles and sang Papageno, Figaro and Leporello in Tokyo (Wolfgang Sawallisch), for the Maggio Musicale Fiorentino (Zubin Mehta), in Zurich (Nikolaus Harnoncourt) and also Masetto at the Metropolitan Opera.

At this point in his career he wished to learn the secrets of the old belcanto. He moved to Venice to study the belcanto technique of Manuel Garcia (whom Richard Wagner admired so much that he wanted him to establish a school in Bayreuth) with Randolph Mickelson, whose association include Joan Sutherland and Montserrat Caballe.

His first major success in this new repertoire was as Gurnemanz in Parsifal for Scottish Opera. He repeated this role to great acclaim at the Tyrol Festival conducted by Gustav Kuhn, in Genova with Michail Jurowski, for the National Theater in Mannheim (Adam Fischer) and for the Opera of South Australia with Jeffrey Tate. He then added the role of Sarastro to his repertoire which he sang for San Francisco Opera and at the Theatre des Champs Elysses in Paris, Baron Ochs in Der Rosenkavalier for Scottish Opera (Richard Armstrong) and Den Norske Opera Oslo (Dietfried Bernet) The Grand Theatre in Marseille (Phillippe Auguin), in Sydney, at the Bolshoi in Moscow, and in Beijing as well as the role of Osmin in Die Entführung aus dem Serail.
In the Italian repertoire Manfred takes great pleasure in singing Ramfis/Aida which he has performed for Scottish Opera and Enrico VIII in Anna Bolena at the Bayrische Staatsoper in Munich (Marcello Viotti), the Finnish National Opera and Pittsburgh Opera. Other roles include Giorgio/I Puritani in Philadelphia, Basilio/Il Barbiere di Siviglia in Munich, Orbazzano/Tancredi at the Staatsoper Berlin (Fabio Luisi).

Manfred Hemm also appears regularly on the concert platform. Particular favourites include the Rossini Stabat Mater and the Verdi Requiem which he sang in Sao Paolo with Isaac Karabchevski. In recent years he sang Beethoven 9th in Stockholm (Herbert Blomstedt), Bruckner Te Deum (Georges Pretre, Eliahu Inbal) and the Dvorak Requiem at the Teatro San Carlo in Naples with Gerd Albrecht.