TMZ said it confirmed his death Wednesday, but the cause was not immediately known.
"He was an amazing person. He was a lot like [his TV character] Mr. Drummond, but much more interesting in real life. He was an amazing father," the actor's daughter, Jennifer, told TMZ, adding Bain spent the last days of his life surrounded by family.
He is also survived by his three sons, as well as his twin brother, Bonar.
"Diff'rent Strokes" was a sitcom about a wealthy white, single dad with a teen-age daughter, who adopts two young African-American boys. It ran for eight seasons from 1978-1985.
Dana Plato and Gary Coleman, who played Bain's on-screen children, both died in recent years. Todd Bridges is the sole surviving lead cast member of the show.
Bain also reprised his role of Mr. Drummond on the sitcoms "The Facts of Life" and "The Fresh Prince of Bel Air," and was a regular cast member on TV's "Maude" and "Mr. President."