He appeared in such films as Charlie Chaplin's A Woman of Paris, where he played the lead role; Stanley Kubrick's Paths of Glory with Kirk Douglas; Ernst Lubitsch's The Marriage Circle; The Sheik with Rudolph Valentino; Morocco with Marlene Dietrich and Gary Cooper; and A Star Is Born with Janet Gaynor and Fredric March, and was nominated for an Academy Award for The Front Page in 1931.

During World War I, he served as a captain in the United States Army Ambulance Service, for which he trained in Pennsylvania before going overseas.

His supporting role in 1923's A Woman of Paris solidified the image of a well-dressed man-about-town, and he was voted Best Dressed Man in America nine times.

The crash of the stock market in 1929 meant that his contract with Paramount was cancelled, but he went on to Metro-Goldwyn-Mayer (MGM) and continued on with films (now talkies) in a variety of ways, with his knowledge of French and Spanish helping at key times, although his starring roles declined by this point.

In 1955, Menjou played Dr. Elliott Harcourt in "Barrier of Silence", episode 19 of the first season of the television series Science Fiction Theatre.

He guest-starred as Fitch, with Orson Bean and Sue Randall as John and Ellen Monroe, in a 1961 episode, "The Secret Life of James Thurber", based on the works of American humorist James Thurber (especially "The Secret Life of Walter Mitty"), in the CBS anthology series The DuPont Show with June Allyson.

"[11] In the 1944 presidential election, he joined other celebrity Republicans at a rally in the Los Angeles Coliseum, organized by studio executive David O. Selznick, to support the Dewey–Bricker ticket and Governor Earl Warren of California, who would be Dewey's running mate in 1948.

The gathering drew 93,000, with Cecil B. DeMille as the master of ceremonies and short speeches by Hedda Hopper and Walt Disney.

[13] Menjou was a leading member of the Motion Picture Alliance for the Preservation of American Ideals, a group formed to oppose "communist influence" in Hollywood, whose other members included John Wayne, Barbara Stanwyck (with whom Menjou costarred in Forbidden in 1932 and Golden Boy in 1939) and her husband, actor Robert Taylor.

Because of his political leanings, Menjou came into conflict with actress Katharine Hepburn, with whom he appeared in Morning Glory, Stage Door, and State of the Union (also starring Spencer Tracy).

"[14] To this, Hepburn called Menjou "wisecracking, witty—a flag-waving super-patriot who invested his American dollars in Canadian bonds and had a thing about Communists.

In German film and theatre, dubious men, opportunists, corrupt politicians, fraudulent persuaders, marriage impostors and other "slick" criminals often wear Menjou-Bärtchen.

In the movie Sunset Boulevard, Joe Gillis arrives to a young adult New Year's Eve party overdressed in a vicuna overcoat and a tailcoat.