Martha Hyer was born in Fort Worth, Texas into a wealthy family, the daughter of Julien Capers Hyer (1894–1974), an attorney and judge, and Agnes Rebecca (née Barnhart; 1892–1969). She was the middle of three sisters, with Agnes Ann (1920–2014) and Jeanne (b. 1928). The Hyers were active in the Methodist church where her father was a highly respected Sunday school teacher. Hyer graduated from Arlington Heights High School and then from Northwestern University with a degree in drama. She was in the sorority Pi Beta Phi with actress Patricia Neal. She then moved to California to study at the Pasadena Playhouse, and soon after was signed to a film contract with RKO. She was married twice, first to producer C. Ray Stahl and later to producer Hal B. Wallis. She converted to Judaism, Wallis’s religion, after their marriage. Wallis and Hyer remained together until his death in 1986. At Northwestern University there is The Hal and Martha Hyer Wallis Blackbox. She had no children. Martha Hyer’s first film appearance was an uncredited speaking part in The Locket (1946). She appeared in uncredited and bit roles in B-movies for the next few years, occasionally working on television as well. Eventually she moved up the ranks, and starting in 1954, began receiving better roles, becoming a popular actress in Hollywood for the next decade.

Martha Hyer had a supporting role in the drama So Big (1953), which stars Jane Wyman, and was directed by Robert Wise. She followed this with westerns, Wyoming Renegades (1954) and The Battle of Rogue River (1954), and a musical comedy, Lucky Me (1954), which stars Doris Day. She then played Elizabeth Tyson, a socialite who almost loses her fiancé (William Holden) to Audrey Hepburn, in the Oscar-winning film Sabrina (1954). She next starred opposite Donald O’Connor in the comedy Francis in the Navy (1955) and in a 1956 televised version of Jezebel for Lux Video Theatre in which she played the lead role of Julie. She had supporting roles in the war story Battle Hymn (1957) with Rock Hudson and in the drama Mister Cory (1957) with Tony Curtis, directed by Blake Edwards. She was featured in Kelly and Me, a comedy with Van Johnson, and as Cordelia Bullock in the 1957 remake of My Man Godfrey with David Niven. In 1958, Hyer appeared in a Playhouse 90 televised version of Reunion by Merle Miller, along with Frances Farmer. She next appeared in Paris Holiday (1958), a comedy with Bob Hope, and Houseboat (1958), an Oscar-nominated film starring Cary Grant. For the 1958 drama Some Came Running, which was directed by Vincente Minnelli and stars Frank Sinatra, Hyer was nominated for the Academy Award for Best Supporting Actress. Soon after, she had supporting roles in the Oscar-nominated films The Big Fisherman (1959) and The Best of Everything (1959), which stars Joan Crawford.

Martha Hyer started the 1960s with a supporting role in Ice Palace (1960), a drama with Richard Burton, and The Last Time I Saw Archie (1961), a comedy with Robert Mitchum. Next she was in A Girl Named Tamiko (1962) with Laurence Harvey, the Oscar-nominated film Wives and Lovers, and the box-office hit The Carpetbaggers (1964). By 1964, Hyer had turned 40 and after a decade of success, she began having trouble finding good roles and worked mainly in television and in European and American B-films. She did appear in two episodes of The Alfred Hitchcock Hour, (A Piece Of Action in 1962 and Crimson Witness in 1965). Also in 1965, she was in The Sons of Katie Elder, a western with John Wayne. She guest-starred on the television series Bewitched as “Margaret Marshall,” a wealthy seductive woman. In 1966, she was in The Chase, which stars Marlon Brando, directed by Arthur Penn. On television, she guest-starred on The Beverly Hillbillies in the episode The Richest Woman, in which she plays “Tracy Richards,” the world’s richest woman. In 1967, she starred in the film drama Some May Live, and in the crime comedy The Happening as the wife of a kidnapped mobster played by Anthony Quinn, and later in the 1969 suspense film Crossplot with Roger Moore. Her final film role was in The Day of the Wolves (1971) and her final television role was in a 1974 episode of McCloud. At age 50, she retired from acting. Martha Hyer enjoyed a quiet retirement through the 1980s and 1990s. She died on May 31, 2014, at the age of 89 from natural causes, in Santa Fe, New Mexico, where she had lived for many years.