Nora Gregor was born in Görz (Gorizia), a Slovenian town which then belonged to Austria-Hungary but is now part of Italy, to Austrian parents. On December 2, 1937, she married Prince Ernst Ruediger von Starhemberg (second husband). In 1938, they emigrated to France through Switzerland. During World War II, she left for Argentina and Chile. She committed suicide in Viña del Mar, Chile, while in exile in South America.
Gregor entered films in the early 1920s. She worked briefly in Hollywood during the early talkie era, appearing in the foreign language versions of such films as The Trial of Mary Dugan and His Glorious Night. Her most famous screen role was as Christine in Jean Renoir's controversial 1939 film La Règle du Jeu. Her last appearance was in the 1945 Chilean film La Fruta mordida.
