[1] She was born in Cleveland, Ohio, to a wealthy family with New England ties (she was descended on her father's side from Mayflower passengers John Alden and Priscilla Mullens and was a great-grandniece of Union General Nathaniel Prentice Banks, Governor of Massachusetts and Speaker of the U.S. House of Representatives).

As a teenager, she and her mother, who served as one of her early vocal coaches, made a recording for Thomas Edison, singing the Flower Duet from the Delibes opera, Lakmé.

[2] A 1926 letter written from France by F. Scott Fitzgerald noted that "Nobody was in Antibes that summer ...except me, Zelda, the Valentinos, the Murphys, Mistinguett, Rex Ingram, Dos Passos, Alice Terry, the MacLeishes, Charlie Brackett, Maud Kahn (daughter of philanthropist Otto Kahn; wife of Major-General Sir John Marriott), Esther Murphy (sister of Gerald; wife of John Strachey), Marguerite Namara, E. Oppenheimer (sic), Mannes the violinist, Floyd Dell, Max and Crystal Eastman, ex-premier Orlando, Etienne de Beaumont ... Just the right place to rough it, an escape from the world.

"[3][4] Stolen Moments, a 1920 silent picture in which she starred with Rudolph Valentino, was one of her few film projects, and it included a small part for her infant daughter Peggy as well.

Later films in which Namara played small parts included Thirty-Day Princess (1934) with Cary Grant and Sylvia Sidney, and Peter Ibbetson (1935) with Gary Cooper and Ann Harding.

In the early 1960s, she and her third husband retired to a secluded ranch house on several acres in California's Carmel Valley, where she painted prolifically and recorded her last album in 1968, the year she turned 80.