Lardner returned to New York and, in 1935, briefly worked at the Daily Mirror before signing on as publicity director with David O. Selznick's new movie company.

Lardner held strong left-wing views, and in the 1930s helped to raise funds for the Republican cause during the Spanish Civil War.

[8] After the Second World War the House Un-American Activities Committee (HUAC) began an investigation into the Hollywood motion picture industry.

Lardner appeared before the HUAC on October 30, 1947, but like Alvah Bessie, Herbert Biberman, Albert Maltz, Adrian Scott, Dalton Trumbo, Lester Cole, Edward Dmytryk, Samuel Ornitz and John Howard Lawson, he refused to answer any questions.

[10] The blacklist was lifted for Lardner when producer Martin Ransohoff and director Norman Jewison gave him screen credit for writing The Cincinnati Kid (1965).

His later work included M*A*S*H (1970), for which he won the Academy Award for Best Adapted Screenplay, and The Greatest (1977), for which he re-wrote the original script by Bill Gunn.

[citation needed] According to Hungarian writer Miklós Vámos—who visited Lardner several times before his death—Lardner won an Academy Award for a movie he wrote under a pseudonym.