She initially studied violin at the University of Music in Freiburg im Breisgau. She then completed singing studies in Karlsruhe, Vienna and Sofia. Initially she presented herself as a soprano and played difficult roles such as the Queen of the Night in Mozart's Die Zauberflöte. During her time as a student in Vienna she got to know large parts of the repertoire in the standing area of ​​the Vienna State Opera. She was given soprano solos in The Creation, The Seasons and Elijah, and one of her first opera roles was at the Junge Oper in Stuttgart, in a children's opera. Then came the switch to mezzo-soprano. She made her debut as Rosina in Il Barbiere di Siviglia at the Schönbrunn Palace Theater (in a production of the Vienna Chamber Opera) and in 2003 went to Lucerne in Switzerland as a member of the ensemble. There she sang a variety of small, medium and large mezzo roles and learned about everyday life on the stage. At the same time, she made guest appearances at the Theater Basel, as Eboli Don Carlo or in 2008 as the title heroine in a Hans Neuenfels production of Schoeck's Penthesilea. This production was voted "Production of the Year" in the critics' survey of the specialist magazine Opernwelt. Baumgartner was a member of the ensemble of the Frankfurt Opera from 2009 to 2020. In the summer of 2010, she made her debut at the Salzburg Festival, where she would take on four central roles in 20th century operas over the years. In 2010 she was Countess Geschwitz in Lulu by Alban Berg, in 2012 Charlotte in Die Soldaten by Bernd Alois Zimmermann, in 2018 Agave in The Bassarids by Hans Werner Henze and in 2020/21 Clytemnästra in Elektra by Richard Strauss. In Frankfurt, she developed a repertoire that ranged from the Baroque to the present day. In Frankfurt, she sang Cornelia in Handel's Giulio Cesare in Egitto, Princess Eboli's Don Carlo and Amneris Aida, Carmen, Charlotte in Massenet's Werther and Tigrana in Puccini's Edgar, the Foreign Princess in Dvořák's Rusalka, a number of Richard Strauss operas, including the Nurse in Die Frau ohne Schatten and Gaea in Daphne, again in the title role of Schoeck's Penthesilea, and in the modern repertoire, Jocaste in Enescu's Oedipe and Gora in the German premiere of Reimann's Medea.

From 2013 onwards, the years of international breakthrough followed: first Clairon in Capriccio at the Royal Opera House Covent Garden and Judith in Bluebeard's Castle at the Edinburgh International Festival, then Brangäne in Tristan und Isolde at the Deutsche Oper Berlin, Judith in Toulouse and Clairon at the Theater an der Wien and finally the role debut as Kostelnička in Jenůfa in Santiago de Chile. The following role debuts were described by the Salzburg Festival as "spectacular" and "acclaimed" - Ortrud Lohengrin at the Hamburg State Opera, Cassandre in Les Troyens at the Frankfurt Opera, Fricka Das Rheingold / Die Walküre at the Bayreuth Festival in 2017 and then at the Lyric Opera of Chicago. In the following years, the singer completed her repertoire with Azucena in Il Trovatore and Maddalena in Rigoletto as well as the Princess of Bouillon in Adriana Lecouvreur. She made her debut with some Wagner roles on opera stages that were new to her - as Kundry in Parsifal at the Vlaamse Opera in Antwerp, at the Grand Théâtre de Genève and at the Canadian Opera Company in Toronto, as Venus in Tannhäuser at the Zurich Opera, as Mary in Der fliegende Holländer at the Bavarian State Opera in Munich. She made a late debut in June 2021 at the Vienna State Opera, as Ortrud in Lohengrin. In June 2024, she took on the role of Angèle Esther in the world premiere of Melancholy of Resistance by Marc-André Dalbavie at the Staatsoper Unter den Linden.

Tanja Ariane Baumgartner is also a concert singer who has performed with the Munich Philharmonic in Munich and Hamburg or with the Orchestre Philharmonique de Radio France in Paris. She sang Mahler's Lied von der Erde and the alto solo in Beethoven's 9th Symphony, most recently in several concerts in Japan. At the Brucknerhaus in Linz she was supposed to take on the role of Giuditta in Mozart's Betulia liberata, but the concert was cancelled due to COVID-19. Instead, she was asked to interpret Gustav Mahler's Das klagende Lied at the 2021 Brucknerfest, accompanied by the Bruckner Orchestra under the direction of Markus Poschner. She sang the alto solo in Beethoven's Missa solemnis in Dresden under the direction of Marek Janowski.