Widmark appeared on Broadway in 1943 in F. Hugh Herbert's Kiss and Tell and in William Saroyan's Get Away Old Man, directed by George Abbott, which ran for 13 performances.

He was in Chicago appearing in a stage production of Dream Girl with June Havoc when 20th Century Fox signed him to a seven-year contract.

[8] In his most notorious scene, Udo pushed a woman in a wheelchair (played by Mildred Dunnock) down a flight of stairs to her death.

Widmark played heroic roles in films, including Down to the Sea in Ships, Slattery's Hurricane (both 1949), and Elia Kazan's Panic in the Streets (1950).

[9] He also featured in Halls of Montezuma (1951) and Don't Bother to Knock (1952) (with Marilyn Monroe), and appeared in two films for director Samuel Fuller: the noir Pickup on South Street (1953) and Cold War drama Hell and High Water (1954).

Widmark continued to appear in a number of successful films, including The Tunnel of Love (1959) with Doris Day, the Westerns Warlock (also 1959) with Henry Fonda, as Jim Bowie in John Wayne's The Alamo (1960), the courtroom drama Judgment at Nuremberg (1961), and reuniting with Sidney Poitier in the adventure The Long Ships (1964).

Widmark produced and starred in the films Time Limit (1957), The Secret Ways (1961) — based on a novel by Alistair MacLean, which Widmark also directed (uncredited) due to clashes with original director Phil Karlson's proposed tongue-in-cheek direction of the screenplay [10] — and The Bedford Incident (1965), his third film with Sidney Poitier and loosely based on the Herman Melville novel Moby Dick.

Widmark received an Emmy Award nomination for his performance as Paul Roudebush, the president of the United States, in the TV movie Vanished!

Widmark began to drift into supporting roles, though he still played the occasional lead, for instance in the 1976 British-West German film To the Devil a Daughter.

Widmark continued to appear in a number of films during the 1980s, again with Sidney Poitier who directed him in the comedy Hanky Panky (1982), with Gene Wilder.

[11] Widmark was married to screenwriter Ora Jean Hazlewood for 55 years from 1942 until her death from Alzheimer's disease in March 1997; they met while attending Lake Forest College.

The couple had one daughter, Anne Heath Widmark, an artist and author who was married to Baseball Hall of Famer Sandy Koufax from 1969 to 1982.

[4] Despite having spent a substantial part of his career appearing in gun-toting roles such as cowboys, police officers, gangsters and soldiers, Widmark disliked firearms and was involved in several gun-control initiatives.