Kirchschlager began her musical training at the Mozarteum in Salzburg, where she studied percussion and piano. In 1984, she went to the Vienna Music Academy, where she studied with Gerhard Kahry and Walter Berry. Her first engagements were at the Wiener Kammeroper and the Graz Opera House. Kirchschlager won third prize in the International Hans Gabor Belvedere Singing Competition in 1991. Her stage debut was in Graz in 1993 as Octavian (Der Rosenkavalier).
In 1993, she became a member of the Vienna State Opera, and made her debut there as Cherubino (The Marriage of Figaro), going on to perofrm Orlofsky (Fledermaus), Rosina (Barbiere di Siviglia), Nicklausse (Contes d’Hoffmann), Octavian (Rosenkavalier), Komponist (Ariadne auf Naxos), Valencienne (Lustige Witwe), Silla (Palestrina), Lauretta (Gianni Schicchi), Stéphano (Roméo et Juliette), Dorabella (Così fan tutte), Clairon (Capriccio), Zerlina (Don Giovanni) as well as the titlerole in the children’s opera Peter Pan. For the Royal Opera House her roles include Melisande (Pelleas et Melisande), Sophie (Sophie’s Choice), Hänsel (Hänsel und Gretel) and Octavian. She performed Sophie as well at the Vienna Volksoper.
In 2007 she was appointed Austrian Kammersängerin.