Trained as a lyric soprano, she began performing at the Metropolitan Opera where she created the role of Genovieffa in the world premiere of Giacomo Puccini's Suor Angelica in 1918.

After performing welfare work in hospitals during World War II, she returned to acting in London in plays by Noël Coward, Terence Rattigan and Shakespeare.

[1] She first became interested in performing around 1910, and in a vocational course began to train her lyric soprano voice under the tutelage of Belgian contralto Freida de Goebele and Italian operatic coach Fernando Tanara.

[2] On Broadway, Ellis played the roles of street urchin and errand girl in Louis in 1921, Nerissa in the 1922 production of Merchant of Venice and The Dancer from Milan in Casanova (1923).

In 1929 she acted the title role in Becky Sharp in the Players' Club adaptation of Vanity Fair, and played Laetitia in 1930 in Children of Darkness.

In London's West End, she starred in Jerome Kern's Music in the Air (1933) and went on to her best remembered roles as the heroines of three Ivor Novello operettas: Glamorous Night (1935), The Dancing Years (1939) and Arc de Triomphe (1943).

[3] Returning to the stage after the war, Ellis was successful in the 1944 and 1947 British productions of Noël Coward's melodrama Point Valaine, playing a hotel keeper in a sordid, clandestine relationship with her head waiter.