Belack was the first actress to play "Bernice Fish", the wife of Detective Fish (played by Abe Vigoda), on the television series Barney Miller, before the role went to actress Florence Stanley. Before that, she was seen mainly in Soap Operas, her best known role being that of the original Anna Wolek Craig on One Life to Live
She played the lead role in the short-lived television sitcom called Baker's Dozen as "Florence Baker", the no-nonsense captain of an undercover anti-crime unit of the N.Y.P.D. The show lasted a month on CBS in 1982. She played Dorothy Zbornak (Bea Arthur)'s sister once on The Golden Girls before the role went to Dena Dietrich. She has had a recurring role on Law & Order as the sharp-tongued "Judge Margaret Barry".