March 1 (UPI) -- Katherine Helmond, who played the sassy, no-nonsense matriarch on Who's the Boss?, died at her home in Los Angeles, her talent agency announced Friday. She was 89.
APA said Helmond died Saturday of complications from Alzheimer's disease.
Perhaps best known for her role as Mona Robinson on the ABC sitcom opposite Tony Danza and Judith Light, Helmond got her start acting in the 1970s, with guest parts on series like Gunsmoke, The Bob Newhart Show and The Bionic Woman. Her film roles at the time included Family Plot and Baby Blue Marine.
Her first big role came in 1977 as Jessica Tate in Soap, a night-time parody of typical melodramatic soap operas. Helmond's starring role in the series was opposite the likes of Robert Mandan, Cathryn Damon, Billy Crystal, Robert Guillaume and Robert Urich.
She would later go on to appear in episodes of Benson and Love Boat before her role in Who's the Boss?, which first aired in 1984. She earned two best supporting actress Emmy nominations for the role.
Alyssa Milano, who played Helmond's granddaughter in the series, celebrated the actor's life by posting clips on Twitter.
"My beautiful, kind, funny, gracious, compassionate, rock. You were an instrumental part of my life. You taught me to hold my head above the marsh! You taught me to do anything for a laugh! What an example you were! Rest In Peace, Katherine," she wrote.
Danza called Helmond a "national treasure" on Twitter.
Helmond had a number of recurring roles on sitcoms in the 1990s and 2000s, including Coach, Everybody Loves Raymond and Providence. Later film roles included Fear and Loathing in Las Vegas, Beethoven's 5th and voice roles on the Cars animated series.