After the war, Derek had a small role in A Double Life (1947) when he was approached by Humphrey Bogart, who renamed him John Derek and cast him as Nick  (Pretty Boy) Romano, an unrepentant killer, in Knock on Any Door (1949), a socially conscious melodrama directed by Nicholas Ray.
Derek was recognized as a talented newcomer, "plainly an idol for the girls", as Bosley Crowther expressed it in a review for The New York Times.
The Los Angeles Times called him "a handsome hot-eyed newcomer who makes the case for this product of the city's slums — 'live fast, die young and have a good looking corpse' — all too fascinating for everybody's comfort."

The film was made for Bogart's Santana company and released through Columbia Pictures, who signed Derek to a seven-year contract in April 1948.

Derek followed that picture with a supporting role as the son of Broderick Crawford in All the King's Men (1949), the Best Picture Oscar winner for its year, starring Broderick Crawford.
In September 1950, the actor had his name formally changed to John Derek.

Columbia promoted him to lead roles, as Robin Hood in Rogues of Sherwood Forest (1950) with Alan Hale; the Los Angeles Times called him a "slim and beautiful youth".
He was meant to follow it with The Gainesville Circus, but the film was never made.

Instead, Columbia put him in another swashbuckler, Mask of the Avenger (1951), then they gave him a good dramatic role in a prestige film, Saturday's Hero (1951), as a college football player.
The novel had been bought specifically as a vehicle for Derek.
He was in a crime noir, The Family Secret (1951), then reunited with Crawford in Scandal Sheet (1952).

Derek was borrowed by Republic Pictures for a war film, Thunderbirds (1952).
He went back to Columbia for Prince of Pirates (1953), a swashbuckler for Sam Katzman; two Westerns, Ambush at Tomahawk Gap (1953), with John Hodiak and The Last Posse (1953) with Crawford.
He was back with Hodiak for Mission Over Korea (1953), a Korean War film, then was again borrowed by Republic for Sea of Lost Ships (1953).
In July 1953, Derek left Columbia.
After the war, Derek had a small role in A Double Life (1947) when he was approached by Humphrey Bogart, who renamed him John Derek and cast him as Nick  (Pretty Boy) Romano, an unrepentant killer, in Knock on Any Door (1949), a socially conscious melodrama directed by Nicholas Ray. Derek was recognized as a talented newcomer, "plainly an idol for the girls", as Bosley Crowther expressed it in a review for The New York Times. The Los Angeles Times called him "a handsome hot-eyed newcomer who makes the case for this product of the city's slums — 'live fast, die young and have a good looking corpse' — all too fascinating for everybody's comfort."
The film was made for Bogart's Santana company and released through Columbia Pictures, who signed Derek to a seven-year contract in April 1948.
Derek followed that picture with a supporting role as the son of Broderick Crawford in All the King's Men (1949), the Best Picture Oscar winner for its year, starring Broderick Crawford. In September 1950, the actor had his name formally changed to John Derek.
Columbia promoted him to lead roles, as Robin Hood in Rogues of Sherwood Forest (1950) with Alan Hale; the Los Angeles Times called him a "slim and beautiful youth". He was meant to follow it with The Gainesville Circus, but the film was never made.
Instead, Columbia put him in another swashbuckler, Mask of the Avenger (1951), then they gave him a good dramatic role in a prestige film, Saturday's Hero (1951), as a college football player. The novel had been bought specifically as a vehicle for Derek. He was in a crime noir, The Family Secret (1951), then reunited with Crawford in Scandal Sheet (1952).
Derek was borrowed by Republic Pictures for a war film, Thunderbirds (1952). He went back to Columbia for Prince of Pirates (1953), a swashbuckler for Sam Katzman; two Westerns, Ambush at Tomahawk Gap (1953), with John Hodiak and The Last Posse (1953) with Crawford. He was back with Hodiak for Mission Over Korea (1953), a Korean War film, then was again borrowed by Republic for Sea of Lost Ships (1953). In July 1953, Derek left Columbia.
John Derek