From left, actors Gary Coleman, Conrad Bain and Todd Bridges speak during the TV Land Awards at the Hollywood Palladium in 2003. (Kevin Winter/Getty Images)

Conrad Bain, a wryly appealing actor who became a household name to millions of TV viewers on the sitcom “Diff’rent Strokes” as a white New York industrialist who adopts two orphans from Harlem, died Jan. 14 in Livermore, Calif. He was 89.

His daughter Jennifer Bain announced the death but did not disclose the cause.

A native of Canada, Mr. Bain graduated in 1948 from the American Academy of Dramatic Arts in New York and became an instantly recognizable supporting player for more than half a century on stage, television and film. With a balding pate and articulate style, he was often cast in well-educated or avuncular roles.

Producer Norman Lear gave Mr. Bain a breakthrough of sorts when he cast the actor as the conservative doctor and next-door neighbor of liberally outspoken Maude Findlay (played by Bea Arthur) on the sitcom “Maude,” which aired on CBS from 1972 to 1978.

Then came “Diff’rent Strokes,” which had its debut on NBC in 1978. Mr. Bain nominally had the leading role of the widowed patriarch Philip Drummond, but he was overshadowed in the popular imagination by the two children his character adopts from his dying black housekeeper.

The young Jackson brood — 8-year-old Arnold and 12-year-old Willis — were played by scene stealers Gary Coleman and Todd Bridges, respectively. Rounding out the family was Mr. Drummond’s daughter, Kimberly, played by Dana Plato.

The show ran until 1986, spending its final year on ABC, but it remained in syndication for many years. “Diff’rent Strokes” charted the usual sitcom story lines about dating and family life and ventured often into race- and class-based humor.

When Mr. Drummond says he owns a hot tub in his Manhattan apartment, Arnold thinks his new millionaire father means the tub is stolen. “If we help you fence it, we get half,” Arnold quips.

At times, the program gained attention for its darker plotlines about child abuse and drug use. First lady Nancy Reagan appeared on a 1983 episode to promote her “Just Say No” anti-drug campaign.

In a sad twist, “Diff’rent Strokes” developed a reputation for the destructive behavior of its child actors. Plato died from a drug overdose at 34 in 1999; Bridges also had a drug addiction and run-ins with the law; and Coleman struggled with financial and legal difficulties until dying in 2010 at 42 of a brain hemorrhage.

“It is really painful,” Mr. Bain told the Los Angeles Times in 1991 as he watched his former castmates struggle. “It leaves you with such a helpless feeling.”

Conrad Stafford Bain was born Feb. 4, 1923, in Lethbridge, Alberta, and was a senior at a high school in Calgary when he appeared in a play for the first time.

He said that show sparked his interest in theater, which led him to New York after Canadian army service during World War II. He became a U.S. citizen in 1946.

As an acting student in New York, he landed small parts on TV anthology shows such as “Studio One.” He later had a recurring role as an innkeeper on the ABC series “Dark Shadows” in the mid-1960s and played a loyal presidential aide to George C. Scott in the short-lived sitcom “Mr. President” (1987).

Mr. Bain was a critical standout as a former anarchist in director Jose Quintero’s landmark 1956 revival of Eugene O’Neill’s tragedy “The Iceman Cometh.” The show, which ran off-Broadway and starred Jason Robards Jr., was four hours, but the power and endurance of the cast were credited with launching a resurgence of interest in O’Neill’s work.

“Conrad Bain’s fanatical philosopher who sees all sides of all questions and is therefore a futile human being is especially well acted,” New York Times theater critic Brooks Atkinson wrote.

Mr. Bain portrayed a Massachusetts senator in the 1961 Broadway production of “Advise and Consent,” based on Allen Drury’s Pulitzer Prize-winning political novel. He played a liberal publisher in “An Enemy of the People” for a 1971 Broadway staging of Arthur Miller’s adaptation of the Henrik Ibsen play.

Two years later, Mr. Bain was an impoverished landowner in Anton Chekhov’s “Uncle Vanya,” directed by Mike Nichols on Broadway in a cast that included Scott, Nicol Williamson and Julie Christie.

Mr. Bain’s final Broadway appearance was as a wise family doctor in a 1991 revival of Paul Osborn’s “On Borrowed Time,” starring Scott as a senior citizen who tries to defy death by trapping him in a tree.

“I sold out and went to TV,” Mr. Bain quipped at the time. “Now I am buying my way back in the theater.”

In 1945, he married Monica Sloan, an artist. She died in 2009. Survivors include three children.

Mr. Bain’s movie career was sporadic but included a memorable appearance as a U.S. government official in Woody Allen’s slapstick comedy “Bananas” (1971).

Mr. Bain was credited as a driving force behind the creation in 1962 of the Actors Federal Credit Union, which helps actors borrow money at low interest rates and obtain credit. “What I wanted to dissipate,” he told the San Diego Union-Tribune years later, “was the legend of the actor as a bad risk, an irresponsible citizen.”