A strong supporter of the House Un-American Activities Committee (HUAC) hearings, Hopper named suspected Communists and was a major proponent of the Hollywood blacklist.

Hearing that Edgar Selwyn was casting his play The Country Boy for a road tour, she went to his office and talked him into letting her audition for the lead.

Her motion picture debut was in The Battle of Hearts (1916) with William Farnum, but she made a major splash in Virtuous Wives (1918), in which she established her pattern of playing society women.

[3] Part of Hopper's public image was her fondness for wearing extravagant hats, for which the Internal Revenue Service allowed her a $5,000 annual tax deduction as a work expense.

Her 1962 book The Whole Truth and Nothing But, which she promoted on the CBS television series What’s My Line?, included a chapter in which Hopper asserted their relationship was a fact.

[10] Hopper was an advocate for actress Joan Crawford, whose career suffered in the early 1940s after she was labelled "Box-Office Poison" and forced to resign from Metro-Goldwyn-Mayer.

In 1945, Hopper reprinted a press release for Mildred Pierce in her column, which described Crawford as a leading contender for the Best Actress Oscar.

[3] Hopper lobbied for African American actor James Baskett to receive an Academy Award for his performance in the 1946 film Song of the South.

[clarification needed] Fairbanks Jr. recalled in his memoirs Salad Days that he was already in uniform serving in the United States Navy, and despised Hopper for her insinuations.

"[15] In 1963, Hopper complained in her column that three out of five Best Actor Oscar nominees were British and only two were American: "The weather's so foul on that tight little isle that, to get in out of the rain, they all gather in theatres and practise Hamlet on each other.

a position as a Hollywood columnist by the Esquire Feature Syndicate due to a recommendation by Andy Hervey of MGM’s publicity department.

[5] When rumors began to surface that Orson Welles’ debut film Citizen Kane was inspired by the life of William Randolph Hearst, Parsons lunched with the director, and believed his evasions and denials.

[5] Hopper arrived uninvited to an early screening of the film and wrote a scathing critique, calling it a "vicious and irresponsible attack on a great man".

[citation needed] In the early 1950s, the Los Angeles Examiner ran on its front page above Parsons's byline: "Ingrid Bergman Baby Due in Three Months at Rome".

Bergman left her husband, neurologist Peter Lindstrom, to live in Italy with director Roberto Rossellini, but the news that she might be pregnant was met with some skepticism.

[5] Louis B. Mayer assisted Hopper in establishing herself as a columnist, and her role was supported by other studio chiefs, which saw it as a step in offsetting Louella's monopolistic power.

During the 1944 presidential election, she spoke before a massive rally organized by David O. Selznick in the Los Angeles Coliseum in support of the Dewey-Bricker ticket, as well as Governor Earl Warren of California, who later became Dewey's running mate in 1948, and later the Chief Justice of the United States.

Others in attendance included Ronald Reagan, Barbara Stanwyck, Ann Sothern, Ginger Rogers, Randolph Scott, Adolphe Menjou, Dick Powell, Gary Cooper, Edward Arnold, and William Bendix.

[21] Hopper strongly supported the House Un-American Activities Committee (HUAC) hearings, and was a guest and speaker of the Women's Division at the 1956 Republican National Convention held in San Francisco to renominate the Eisenhower–Nixon ticket.

[22] She was so well known for her conservatism that rumor had it she planned to stand up, unfurl an American flag, and walk out of the 23rd Academy Awards ceremony in March 1951 if Jose Ferrer, who was known to be a socialist, should win Best Actor.

[6][23] She was a leading member of the Motion Picture Alliance for the Preservation of American Ideals, founded in 1944 and devoted to rooting out suspected Communists in Hollywood.

[24][25] She considered herself to be a guardian of moral standards in Hollywood and bragged that she need only wag her finger at a producer and he would break off an adulterous affair instantly.

Charlie Chaplin was another target of Hedda Hopper's vitriol because of his alleged Communist sympathies and his relationships with much younger women, which she considered immoral despite her own marriage to a man 27 years her senior.

"[3] Her grudge deepened when, later in the year, Chaplin married 18-year old Oona O'Neill and gave the scoop to Louella Parsons out of dislike for Hopper.

[6] Seeking revenge, Hopper launched a PR campaign decrying Bergman for being pregnant out of wedlock and carrying a married man's child.

[19] Hopper had an acting role in a radio soap opera, playing Portia Brent on the Blue Network's Brenthouse beginning in February 1939.

This program featured music, talk and dramatized excerpts from movies with well-known guests, such as Broderick Crawford reprising a scene from All the King's Men (1949).

Hosted by Hopper, guest interviews included an eclectic mix of past, current and future stars: Lucille Ball, Francis X. Bushman, Liza Minnelli, John Cassavetes, Robert Cummings, Marion Davies, Walt Disney, Janet Gaynor, Bob Hope, Hope Lange, Anthony Perkins, Debbie Reynolds, James Stewart, and Gloria Swanson.