On television, two of his best-known roles were those of bachelor-uncle-turned-reluctant-parent Bill Davis in the 1960s sitcom Family Affair, and a tough retired judge in the lighthearted 1980s crime drama Hardcastle and McCormick.

He also starred in The Brian Keith Show, which aired on NBC from 1972 to 1974, where he portrayed a pediatrician who operated a free clinic on Oahu, and in the CBS comedy series Heartland.

He served during World War II as a radioman/tail gunner in the rear cockpit of a two-man Douglas SBD Dauntless dive bomber in a U.S. Marine squadron.

[5] He began to guest star on shows such as Hands of Mystery, Shadow of the Cloak, and an adaptation of Twenty Thousand Leagues Under the Seas in Tales of Tomorrow.

[7] Keith guest starred on Campbell Summer Soundstage, The Pepsi-Cola Playhouse, Lux Video Theatre, and The Mask and also played Mike Hammer in a television pilot directed by Blake Edwards, but the series was not picked up.

He was top billed in Chicago Confidential (1957), but returned to supporting parts with Appointment with a Shadow (1957) Hell Canyon Outlaws (1957), and Fort Dobbs (1958).

[11] Keith was top billed in some low-budget action movies: Violent Road (1958), Desert Hell (1958), Sierra Baron (1958), and Villa!!

[12][13] He guest starred on Studio One in Hollywood, Rawhide, Laramie, Alfred Hitchcock Presents, and an episode of Zane Grey Theater, which was written and directed by Sam Peckinpah and later led to The Westerner.

Keith supported Paul Newman in The Young Philadelphians (1959), and had the lead in two productions for Disney, the TV show Elfego Baca: Move Along, Mustangers (1959) and the feature Ten Who Dared (1960).

"[14] Keith guest starred in: The Untouchables, The Americans, Frontier Circus, Alcoa Premiere, Outlaws, Follow the Sun, and Alfred Hitchcock Presents again.

He guest starred on Target: The Corruptors, The Alfred Hitchcock Hour, The Virginian, Sam Benedict, Dr. Kildare, The Fugitive, Wagon Train, 77 Sunset Strip, Kraft Suspense Theatre, The Great Adventure, and Profiles in Courage.

Keith did a Western for Universal, The Raiders (1963), then returned to Disney for Johnny Shiloh (1963), Bristle Face (1964), The Tenderfoot (1964), A Tiger Walks (1964), and Those Calloways (1965).

He went to Fox for The Pleasure Seekers (1964) and had support roles in The Hallelujah Trail (1965), The Rare Breed (1966) (again with O'Hara), and Nevada Smith (1966), co-starring with Steve McQueen as traveling gunsmith Jonas Cord.

In 1966, Keith landed the role of Uncle Bill Davis on CBS's popular television situation comedy Family Affair.

So, he was a very interesting character and it was Brian and Sebastian Cabot [who played Mr. French] had such a different style of acting and that's another reason I think that Family Affair was so popular and stayed as it did.

[14] Keith made Scandalous John (1971) for Disney, Something Big (1972) with Dean Martin and director Andrew McLaglen, and the TV movie Second Chance (1972).

[14] Keith also starred in the role of Steven "The Fox" Halliday in the six-part television miniseries, The Zoo Gang (1974), about a group of former underground French Resistance fighters from World War II.

He replaced Barnard Hughes on Broadway in Da and was on The Seekers (1979), Power (1980), The Silent Lovers (1980), The Mountain Men (1980) with Charlton Heston, and Charlie Chan and the Curse of the Dragon Queen (1981).

Keith starred in The Alamo: Thirteen Days to Glory (1987) (as Davy Crockett), and Death Before Dishonor, then did another TV series Pursuit of Happiness (1987–88), which ran 10 episodes.

Keith made a guest appearance in the Evening Shade season-one episode "Chip Off The Old Brick" (1991), as the loud-mouthed father of Herman Stiles (played by actor Michael Jeter).

He reprised his character from The Westerner in The Gambler Returns: The Luck of the Draw (1991) (which featured numerous actors from 1950s TV series playing their original roles in brief cameos), had the lead in Walter & Emily (1991), a short-lived sitcom, and The Streets of Beverly Hills (1992), a pilot.

Keith performed the role of Mullibok on the Star Trek: Deep Space Nine season-one episode entitled "Progress" (1993), in which an elderly farmer resists forcible relocation by Bajoran authorities.