After she won the 1931 Miss New Orleans beauty contest, she and her mother moved to Chicago, where Lamour earned $17 a week as an elevator operator for the Marshall Field department store on State Street. She had no training as a singer but was persuaded by a friend to try out for a female vocalist's spot with Herbie Kay, a band leader who had a national radio show called "The Yeast Foamers", apparently because it was sponsored by Fleischmann's Yeast.
She left Kay's group and moved to Manhattan, where Rudy Vallee, then a popular singer, helped her get a singing job at a popular night club, El Morocco. She later worked at 1 Fifth Avenue, a cabaret where she met Louis B. Mayer, the Hollywood studio chief. It was Mayer who eventually arranged for her to have a screen test, which led to her Paramount contract in 1935.
In 1935, she had her own fifteen-minute weekly musical program on NBC Radio. She also sang on the popular Rudy Vallee radio show. When she was at her zenith as a star, her fans suggested that an agent had adopted her last name from the French word for "love" as a box-office ploy. In fact, the name was close to one in the family; Lamour adapted it herself from Lambour, which was the last name of her stepfather, Clarence.
Early in her career, Lamour met J. Edgar Hoover, director of the Federal Bureau of Investigations. According to Hoover's biographer Richard Hack, Hoover pursued Lamour romantically, but she was initially interested only in friendship with him. Hoover and Lamour remained close friends to the end of Hoover's life, and after his 1972 death, Lamour did not deny rumors that she'd had an affair with him in the years after she divorced Kay.
She appeared in the classic series of "Road to..." movies, such as Road to Morocco, also starring Bing Crosby and Bob Hope in the 1940s and 1950s. The movies were enormously popular during the 1940s, and they regularly placed among the very top moneymaking films each year as a new one came out. While the films centered more on the talents of Hope and Crosby, Lamour held her own as their "straight man", looked beautiful, and sang some of her most popular songs. Her appearance in the films was considered by the public and theater owners of equal importance to the contributions of Crosby and Hope during the series' golden era, 1940-1952. It was only after the series was essentially over with the release of Road to Bali in 1952 and her career declining while co-stars Hope and Crosby remained major show business figures that her contributions to the series began being downplayed by journalists. During the World War II years, Lamour was among the most popular pinup girls among American servicemen, along with Betty Grable, Rita Hayworth, and Lana Turner. Lamour was also largely responsible for starting up the war bond tours in which movie stars would travel the country selling war bonds for the U.S. Government to the public. Lamour alone promoted the sale of over $21 million dollars worth of war bonds, and other stars promoted the sale of a billion more.
Some of Dorothy Lamour's other notable films include John Ford's The Hurricane (1937), Spawn of the North (1938), Disputed Passage (1939), Johnny Apollo (1940), Aloma of the South Seas (1941), Beyond the Blue Horizon (1942), Dixie (1943), A Medal for Benny (1945), My Favorite Brunette (1947), On Our Merry Way (1948) and the best picture Oscar-winner The Greatest Show on Earth (1952). Her leading men included William Holden, Tyrone Power, Ray Milland, Henry Fonda, Jack Benny, George Raft, and Fred MacMurray.
Dorothy Lamour starred in a number of movie musicals and sang in many of her comedies and dramatic films as well, introducing a number of standards including "The Moon of Manakoora", "I Remember You", "It Could Happen to You", "Personality", and "But Beautiful". Lamour's film career petered out in the early 1950s and she began a new career as a nightclub entertainer and occasional stage actress. In the 1960s she returned to the screen for secondary roles in three films and became more active in the legitimate theater, headlining a road company of Hello Dolly! for over a year near the end of the decade.
As she entered her late seventies, in 1990, she made only a handful of professional appearances but she remained a popular interview subject for publications and TV talk and news programs. In 1995 the musical Swinging on a Star, a revue of songs written by Johnny Burke opened on Broadway and ran for three months; Lamour was credited as a "special advisor" in the credits. Burke wrote many of the most famous "Road to..." movie songs as well as the score to Lamour's And the Angels Sing. The musical only ran three months but was nominated for the Best Musical Tony Award and the actress playing "Dorothy Lamour" in the Road movie segment, Kathy Fitzgerald was also nominated.
Lamour died at her home in North Hollywood, California at the age of 81 from a heart attack. She was interred in the Forest Lawn, Hollywood Hills Cemetery in Los Angeles, California, after a Catholic funeral service.