She started out in the 1940s as co-manager, with her brother Owen, of the Vieux Carre Restaurant on Bourbon Street. She had the menu printed in English instead of French, added local Creole dishes, and became an authority on wine. In 1954, they bought an 18th-century building in the French Quarter and opened Brennan's Restaurant. In 1969, she and a sister, Adelaide Brennan, bought a run-down place called Commander's Palace and improved it to the point of national fame and reputation.