Mary Mills made her professional debut at the Houston Grand Opera. She has since appeared with the San Francisco Opera in several productions including the world premiere of Dangerous Liaisons in which she created the role of Cecile de Volanges (the production was taped for broadcast on PBS and for commercial release), La Bohème, Don Giovanni, Carmen and Arabella. Ms. Mills made her acclaimed 1994 Metropolitan Opera debut as Zdenka and returned to the Met during the 1996-97 season in Franco Zeffirelli's staging of La Bohème as Mimi, a role she has also sung in San Francisco, Detroit, Santiago de Chile, Antwerp (Belgium) and Geneva. She has also been a frequent guest to the Washington Opera, Philadelphia Opera, Pittsburg Opera, Florida Grand Opera, Michican Opera, Dallas Opera, St. Louis and many others in a wide variety of roles which have included Micaela, Susanna, the title role in Janacek's The Cunning Little Vixen, Marguerite, the title role in L'Incoronazione di Poppea and Nedda.
Mary Mills made her European debut as Charpentier's Louise in Geneva in 1992; a success that immediately resulted in invitations to the renowned Wexford Festival in Ireland (Camille in Herold's Zampa) and the Bregenz Festival (Olga in Giordano's Fedora). The artist made her debut at the Bastille in 1997 in the title role of Massenet's Manon, and was re-engaged in the same theatre to sing Micaela in Carmen in the 1999/2000 season. She has also been heard in Antwerp in Gounod's Romeo et Juliette, and Antonia in Les Contes d'Hoffmann in Santiago, Chile and as Mimi in La Bohème at the Opera National du Rhin. In the 1999 season, she also sang Marguerite in a new production of Gounod’s Faust at the Opéra de Lyon. In the course of the 2002/2003 season, she returned to the Metropolitan Opera (Carmen) and the Opéra Bastille (Faust) and has since made her debut at the Berlin Staatsoper, Mimi (La Bohème), the Opera de Monte-Carlo (Manon), Bilbao (Manon).
As her repertoire evolves, Ms Mills sang in 2004 her first Katya Kabanova at Theatre Saint Gallen, Switzerland to great acclaim and could also be heard in the same year at Vienna Festival for Smetana’s Dalibor. In June 2006, she returned to the Berlin Staatsoper (La Bohème) and sang the role of Stella in A Streetcar Named Desire at the Theater an der Wien. During the 2008-2009 season, she sang a new production of Braunfels’ Szenen aus dem Leben der Heiligen Johanna at the Deutsche Oper in Berlin, Dr Faust at the Teatro de la Maestranza and Lohengrin at the Würtembergische Staatstheater in Stuttgart.
Last season, Mary Mills returned to Stuttgart to sing Katya Kabanova and performed opera arias with the Tchaikovsky Symphony Orchestra in Moscow. She also sang La Bohème at the Deutsche Oper Berlin. She will begin the 2010-2011 season with Honegger’s Jeanne d’Arc au Bûcher at the Deutsche Oper Berlin. She will then perform Lehár’s Das Fürstenkind with the Münchner Rundfunkorchester.