William studied at Harvard University (1882–1885), but was expelled for sending faculty members chamber pots with the recipient's picture adorning the inside bottom. Searching for an occupation, in 1887 he took over management of a newspaper which his father had accepted as payment of a gambling debt, the San Francisco Examiner. Giving his paper a grand motto, "Monarch of the Dailies", he acquired the best equipment and the most talented writers of the time. A self-proclaimed populist, Hearst went on to publish stories of municipal and financial corruption, often attacking companies in which his own family held an interest. Within a few years, his paper dominated the San Francisco market. In 1895, with the financial support of his mother, Hearst bought the failing New York Morning Journal, hiring writers like Stephen Crane and Julian Hawthorne and entering into a head-to-head circulation war with his former mentor, Joseph Pulitzer, owner of the New York World, from whom he 'stole' Richard F. Outcault, the inventor of color comics. His was the only major newspaper in the East to support William Jennings Bryan and Bimetallism in 1896. The New York Journal (later New York Journal-American) reduced its price to one cent and attained unprecedented levels of circulation through sensational and dishonest articles on subjects like crime and pseudoscience; The paper's bellicosity in foreign affairs was notorious — on the Cuban Insurrection, for example. Both Hearst and Pulitzer published images of Spanish troops placing Cubans into concentration camps where they suffered and died from disease and hunger. The term yellow journalism, which was derived from the name of "The Yellow Kid" comic strip in the Journal, was used to refer to the sensational style of newspaper articles that resulted from this competition. Journalism historians point out that Yellow Journalism was rare outside New York City in 1898, and is unlikely to have affected voters outside Gotham. Hearst did not cause the Spanish-American War of 1898, but he certainly publicized it try to sell more copies than his rival Pulitzer. They both reached a million copies a day. His own political career suffered after the assassination of President William McKinley when a satirical poem by Ambrose Bierce he had published a few months earlier alluding to a possible McKinley assassination made the publisher look irresponsible. Cartoonist Rogers in 1906 sees the political uses of Oz: he depicts William Randolph Hearst as Scarecrow stuck in his own Ooze in Harper's Weekly In part to aid in his political ambitions, Hearst opened newspapers in other cities, among them Chicago, Los Angeles and Boston. By the mid-1920s he had a nation-wide string of 28 newspapers, among them the Los Angeles Examiner, the Boston American, the Chicago Examiner, the Detroit Times, the Seattle Post-Intelligencer and the Washington Times and Washington Herald and his flagship the San Francisco Examiner. In 1924 he opened the New York Daily Mirror, a racy tabloid frankly imitating the New York Daily News. Among his other holdings were the magazines Cosmopolitan, and Harper's Bazaar; two news services, Universal News and International News Service; King Features Syndicate; a film company, Cosmopolitan Productions; extensive New York City real estate; and thousands of acres of land in California and Mexico, along with timber and mining interests.

Though he served two terms in the US Congress, Hearst's political ambitions were mostly frustrated. Conceding an end to his political hopes, he became involved in an affair with film actress Marion Davies, and from about 1919 he lived openly with her in California, while his wife, Millicent (who had herself been a vaudeville performer before their marriage in 1903), and five sons remained in New York. Millicent, who remained married to William until his death and who was reportedly highly respected by him for her spirit and strength, built an independent life for herself in New York City as a leading philanthropist, was active in society, and created the Free Milk Fund for the poor in 1921.