Peter Finch was desperate to win the role of Howard Beale once he had read the script. He even offered to pay his own airfare to New York City for the screentest. But Sidney Lumet was concerned about Finch's Australian accent. Finch won the part after sending Lumet a recording of himself reading the New York Times with a perfect American accent.

According to Sidney Lumet, the "Mad as Hell" speech was filmed in one and a half takes. Midway through the second take, Peter Finch abruptly stopped in exhaustion. Lumet was unaware of Finch's failing heart at the time, but in any case, did not ask for a third take. The complete film features the second half of the first take and the first half of the second take.

Beatrice Straight is only on-screen for five minutes and two seconds. Hers was the briefest performance ever to win an Oscar.

Peter Finch died before the Academy Awards were to take place, where he was nominated for Best Actor. He won, making him the first performer ever to receive a posthumous award at the Oscars. The second winner was fellow Australian Heath Ledger for The Dark Knight (2008).

Director Sidney Lumet and screenwriter Paddy Chayefsky claimed that the film was not meant to be a satire but a reflection of what was really happening.