Schumann-Heink made her debut in Dresden, Germany, in 1878 as Azucena in Giuseppe Verdi's Il trovatore. She sang in Wagnerian operas in Bayreuth, Germany, between 1896 and 1906 and created the role of Klytemnestra in Strauss's Elektra in 1909. From 1899 to 1904 she sang at the Metropolitan Opera in New York City. She often gave recitals and once toured the United States with the operetta Love's Lottery. Although known primarily as a Wagnerian singer—her most noted role was Erda in Wagner's Siegfried—her repertory included about 150 roles, among them Georges Bizet's Carmen, Fidès in Giacomo Meyerbeer's Le Prophète, and Orlovsky in Die Fledermaus by Johann Strauss. In the latter part of her life she was known for her radio broadcasts in the United States, and she appeared in the film Here's to Romances (1935).

Schumann-Heink, who took the names of two of her husbands, Ernst Heink and Paul Schumann, enjoyed a remarkably long career. In her prime she was considered the greatest contralto in the world, and in addition to her operatic work she was a notable interpreter of lieder. Her powerful, rich voice of remarkable range, her command of the grand manner, and her personal warmth and manifest kindliness made her a favourite with audiences for nearly a half century.