Day was born La Raine Johnson in Roosevelt, Utah, one of eight children in an affluent Mormon family. She had a twin brother, Lamar. The family later moved to California where she began her acting career with the Long Beach Players. She was a 1938 graduate of Polytechnic High School in Long Beach, California.
In 1937, Day debuted onscreen in a bit part in Stella Dallas. Shortly afterwards, she won lead roles in several George O’Brien westerns at RKO, in which she was billed as “Laraine Hays” and then “Laraine Johnson”. In 1939 she signed with MGM, and became popular and well-known (billed as Laraine Day) as “Nurse Mary Lamont”, the title character’s fiancee in a string of seven “Dr. Kildare” movies beginning with Calling Dr. Kildare (1939), with Lew Ayres in the title role. Her roles for other studios were often far more stimulating than those MGM gave her, including a prominent supporting part in the Irish melodrama My Son, My Son! (1940). She also starred in the Alfred Hitchcock thriller Foreign Correspondent (1940) with Joel McCrea, and the psychological mystery The Locket (1946) with Robert Mitchum, Brian Aherne, and Gene Raymond. In 1941 she was voted the number one “star of tomorrow” in Hollywood.

She was paired opposite major film stars, including Lana Turner, Cary Grant, and John Wayne, and hosted a TV show alternately called Daydreaming With Laraine or The Laraine Day Show (1951). During a time when she had a break in her film career she made her stage debut opposite Gregory Peck in the national theatre tour of Angel Street. She also made other stage appearances in Lost Horizon, the 1973 revival of The Women, and a revival of The Time of the Cuckoo.[4] In the 1940s she made guest appearances on radio in both Lux Radio Theatre and The Screen Guild Theater. Day’s first marriage was to singer turned airport executive, James Ray Hendricks in 1942. The couple adopted three children: Christopher, Angela and Michelle. Day filed for divorce from Hendricks in December 1946. Day was granted an interlocutory divorce from Hendricks on January 20, 1947, which required her to wait one year before remarrying. On January 21, 1947, Day traveled to Juarez, Mexico where she received a second divorce decree. Later that day, she traveled to El Paso, Texas, where she married baseball manager Leo Durocher. Upon returning to California, the judge who granted Day’s interlocutory divorce from Hendricks stated that the Mexican divorce she received was not legal and, since she failed to wait the one year period for her divorce to become final, deemed her Texas marriage illegal as well. After waiting approximately one year, Day and Durocher remarried on February 16, 1948, in Santa Monica, California. During her marriage to Durocher, Day was often referred to as “The First Lady of Baseball”. While Durocher was managing the New York Giants, she wrote, Day With the Giants (1952). In 1952, she wrote and published another book entitled The America We Love. She was also the host of Day With the Giants, a 15-minute television interview program broadcast before New York Giants home games. Day and Durocher divorced in June 1960.

On March 7, 1961, Day married television producer Michael Grilikhes. She and Grilikhes had two daughters, Dana Laraine (born November 13, 1962) and Gigi (born October 6, 1964). After their births, Day rarely appeared in films, and only occasionally appeared on TV, usually portraying matronly types. In October 1960, Day appeared in the Nixon-Lodge Bumper Sticker Motorcade Campaign in Los Angeles along with Ginger Rogers, Cesar Romero, Irene Dunne, Dick Powell, Mary Pickford and John Payne. In the 1970s she was the spokesperson for the Make America Better campaign and traveled across the country sharing her views on environmental issues.[19] In that same period of time she was active in establishing a playhouse in Los Angeles for Mormon actors and she helped bring Ray Bradbury’s work the attention of the public. Day had moved back to her native Utah in March 2007 following the death of her third husband. She died at her daughter Gigi’s home in Ivins, Utah, on November 10, 2007, at the age of 87. Following her death her body was taken back to California and on November 15, 2007, a memorial service was held at Forest Lawn Memorial Park in the Hollywood Hills.
For her contribution to the motion picture industry, Laraine Day has a star on the Hollywood Walk of Fame at 6676 Hollywood Blvd.