The star - who was best known for her role as Edith Fairchild in the US daytime soap - passed away on June 24th at the Cedars-Sinai Medical Center in Los Angeles.
According to The Hollywood Reporter, a family spokesperson revealed Joan died of complications from a stroke.
As well as 'General Hospital', Joan also appeared in US soap operas 'Days of Our Lives' and 'Capitol', and was known for starring in the likes of variety programme 'The Steve Allen Show', and the original version of 'Candid Camera', in which she played a lost tourist seeking directions.
What's more, she made TV appearances in 'The Incredible Hulk', 'Fantasy Island', 'The Smith Family', 'Apple's Way', among others.
Joan was married to 'How to Succeed in Business Without Really Trying' actor John Myhers from 1962 until his passing in 1992, and she went on to wed 'On the Waterfront' star Rod Steiger - who won an Academy Award for Best Actor for his role in 1967 movie 'In the Heat of the Night' - in 2000.
They were together until his death in 2002, aged 77.
Following Rod's passing, Joan formed a relationship with actor Jeremy Slate until he died in 2006 aged 80.
Speaking in 2016 about her relationships, Joan said: "Strangely, I met all three of these men when I was in New York, just beginning my career while I was still a teenager.
"Both of my husbands, and my lifetime partner Jeremy, were wonderful men who respected me as an actress.
"They all died from different forms of cancer, so my memories are sometimes bittersweet, but with no regrets."
Joan appeared alongside Rod in 2001 movie 'A Month of Sundays', which was one of his final film roles.