Director Anatole Litvak scheduled the hospital scenes first in the shooting schedule for The Snake Pit, then gave Olivia de Havilland a month-long break before filming the flashbacks. For the hospital scenes, he gave orders that none of the actresses playing patients were to wear brassieres or girdles. He also forbade them to go to the hairdressing department. To make her character look suitably ill, Olivia de Havilland went on a diet designed to take her below her ideal weight.

Although publicity and some later accounts claim The Snake Pit was shot almost entirely at Camarillo State Hospital in California, there were only a few location scenes shot there. Most of the interiors were shot on the 20th Century-Fox lot.

For the flashbacks to de Havilland's life before institutionalization, she wore clothes two sizes too large. Litvak also had her dark eyebrows blotted with powder to de-glamorize her look.

For filming of the sequences in the mental hospital, Dr. Sidney Loseef Tamarin and Dr. Alma Margaret Comer worked on set as technical consultants.

Although Fox's ads for The Snake Pit linked it to Gentleman's Agreement (1947) as a pioneering social problem film, posters also tried to created a romantic angle with the line "Married and in Love...with a Man She Didn't Know or Want!"

Ads during the film's initial run warned parents that the film might not be suitable for children. New York Times film critic Bosley Crowther seconded that opinion and in one column suggested the film only be shown in smaller theatres. Fox did not follow his advice.

The Snake Pit was held back from distribution in England for a year because the British Board of Film Censors forbade films dealing with insanity. Initially, efforts to soften that stand were fought by nursing organizations, who feared the film would discourage young women from going into that profession. Finally, Fox cut the most extreme scenes of de Havilland's treatment to get past the censors. They also included a written prologue explaining that all of the cast were actors and that the film did not reflect conditions in British mental hospitals. The Snake Pit then won rave reviews in England and broke box office records.

by Frank Miller