Sutherland announced his mother's death on Twitter, saying she succumbed to complications surrounding pneumonia.
"Sadly she had been battling for her health for quite some time and we, as a family, knew this day was coming", he writes.
She has appeared in films from acclaimed filmmakers such as Stanley Kubrick's Lolita (1962) and David Cronenberg's Dead Ringers (1988).
Douglas, who celebrated her birthday three days ago, was married to actor Donald Sutherland from 1966-1971. Her father, Tommy Douglas, was a well-known Canadian statesman and the first leader of the federal New Democratic Party.
Over the course of her lifetime, the actress received a number of accolades for her work, including the Gemini Award in 2000 for her work in Shadlow Lake and the International Achievement Award in 2000. In 2013, Douglas said of her dad, "He was such a great speaker". She graduated from the Royal Academy of Dramatic Art in London in 1952 and worked in England before returning to Canada in 1957. She was an ally to immigrants, advocated for women and established the fundraising group "Friends of the Black Panthers".
Douglas, though, was foremost a champion for Canada's medicare system. Her support for the group brought controversy, though - she was refused a USA work permit and arrested in 1969 on conspiracy charges of possessing unregistered explosives.
Canadian actor Art Hindle recalled Douglas as a "loving wife and mother" who was also "a fierce activist who guided me and so many others in our activism".
The Canadian activist received numerous awards and honours throughout her life, including the Order of Canada. She also had a starring role as the family matriarch in the comedy series Wind at My Back, which ran between 1996 and 2001.
"Because of her, Ontario has strict laws protecting all children working in theatre, film and TV".