"Hitch told me I was going to play a nymphomaniac," Fleming said later. "I remember rushing home to look it up in the dictionary and being quite shocked." The film was popular and Selznick gave her another good role in a thriller, The Spiral Staircase (1946), directed by Robert Siodmak. Selznick then lent her out to appear in supporting parts in the Randolph Scott Western Abilene Town (1946) at United Artists, and the film noir classic Out of the Past (1947) with Robert Mitchum, at RKO.
Fleming's first leading role came in Adventure Island (1947), a low-budget action film made for Pine-Thomas Productions at Paramount in the two-color Cinecolor process and co-starring fellow Selznick contractee Rory Calhoun.
She then played another leading role opposite a comedian, in this case Bob Hope, for The Great Lover (1949). It was a big hit and Fleming was established.
"After that, I wasn't fortunate enough to get good directors," said Fleming. "I made the mistake of doing lesser films for good money. I was hot - they all wanted me - but I didn't have the guidance or background to judge for myself."
She was John Payne's love interest in The Eagle and the Hawk (1950), a Western. In February 1949, Selznick had sold his contract players to Warner Bros, but he kept Fleming. Fleming was lent to RKO to play a femme fatale opposite Dick Powell in Cry Danger (1951), a film noir. Back at Paramount, she played the title role in a Western with Glenn Ford, The Redhead and the Cowboy (1951).