She started off with a spell in a convent but decided to go into the family business. Independent, cultured, ironic and outspoken, Constance, the first Bennett sister to enter motion pictures, appeared in New York-produced silent movies before a meeting with Samuel Goldwyn led to her Hollywood debut in Cytherea (1924).
She abandoned a burgeoning career in silents for marriage to Philip Plant in 1925; She resumed her film career after divorce, with the advent of talking pictures (1929), and with her delicate blonde features and glamorous fashion style, quickly became a popular film star.
In 1931, a short-lived contract with Metro Goldwyn Mayer earned her $300,000 for two movies which included The Easiest Way and made her one of the highest paid stars in Hollywood. The next year she moved to RKO, where she acted in What Price Hollywood? (1932), directed by George Cukor, an ironic and at the same time tragic behind-the-scenes looks at the old Hollywood studio system, in which she gave her finest performance. In this movie she is a star-struck waitress, named Mary Evans, who manages to make a good impression on a prominent film director (played by Lowell Sherman); with his patronage she becomes a movie star. While the director has some serious alcohol problems, she marries a wealthy playboy (played by Neil Hamilton), who genuinely loves his wife but is jealous of the demands made on her by her career. He leaves her, but not before Mary has been impregnated. She begins to turn her attentions to her mentor, but it is too late: he kills himself in her bedroom. Hoping to heal her emotional wounds, Mary flees to Paris with her child, where she is reunited with her contrite husband.
Bennett next showed her versatility in the likes of Our Betters (1933), Bed of Roses (1933) with Pert Kelton, The Affairs of Cellini (1934), After Office Hours (1935) with Clark Gable, the original Topper (1937, in a career standout as Marian Kerby opposite Cary Grant, a role she repeated in the 1939 sequel, Topper Takes a Trip), the ultimate madcap family comedy Merrily We Live (1938) and Two-Faced Woman (1941, supporting Greta Garbo).
By the 1940s, Bennett was working less frequently in film but was in demand in both radio and theatre. Shrewd investments had made her a wealthy woman, and she founded a cosmetics and clothing company.
After World War II
She had a major supporting role in Warner Bros.'s The Unsuspected (1947) opposite Claude Rains, in which she played the program director who helps prove that Rains is guilty of murder. She made no films from the early 1950s until 1965 when she made a comeback in the film Madame X (released posthumously in 1966) playing Lana Turner's mother-in-law. Shortly after filming was completed, Bennett collapsed and died from a cerebral hemorrhage at the age of 60.
In recognition of her military contributions, and as the wife of Theron John Coulter, who had achieved the rank of brigadier general, she was buried in Arlington National Cemetery. Coulter died in 1995 and was buried with her.
Bennett has a star on the Hollywood Walk of Fame for her contribution to motion pictures, at 6250 Hollywood Boulevard, a short distance from the star of her sister, Joan.
Bennett was married five times.
- In 1921 Bennett eloped with Chester Hirst Moorehead of Chicago, the son of a surgeon. The marriage was annulled in 1923.
- Bennett eloped with millionaire socialite Philip Morgan Plant (died 1941) in 1925; they divorced in 1929. In 1932, Bennett brought back from Europe a three-year-old child, whom she claimed to have adopted and named Peter Bennett Plant. In 1942, however, during a battle over a large trust fund established to benefit any descendants of her former husband, Bennett announced that her adopted son actually was her natural child by Plant, born after the divorce and kept hidden in order to ensure that the child's biological father did not get custody. During the court hearings, the actress told her former mother-in-law and her husband's widow that "if she got to the witness stand she would give a complete account of her life with Plant. The matter was settled out of court."
- She captured numerous headlines in 1931, when she married one of Gloria Swanson's former husbands, Henri le Bailly, the Marquis de La Coudraye de La Falaise (1898–1972), a French nobleman and film director. Bennett and de la Falaise founded Bennett Pictures Corp. and co-produced two films which were the last filmed in Hollywood in the two-strip Technicolor process,Legong: Dance of the Virgins (1935) filmed in Bali, and Kilou the Killer Tiger (1936), filmed in Indochina. They were divorced in 1940.
- In 1941, Bennett married the actor Gilbert Roland, by whom she had two daughters, Lorinda and Christina (a.k.a. Gyl). They were divorced in 1946.
- In June 1946, Bennett married US Air Force Colonel (later Brigadier General) John Theron Coulter (1912–1995). After her marriage, she concentrated her efforts on providing relief entertainment to US troops still stationed in Europe, winning military honors for her services.
- She was the aunt of Morton Downey Jr.