Famed for TV shows such as Australia’s Next Top Model, the New Zealand-born star had a history of depression.
She was found dead in her Sydney flat on Saturday morning. Police said there were no suspicious circumstances.
In 2012, she was admitted to a Sydney hospital after a suicide attempt following an ongoing tirade of abuse on Twitter.
She revealed in her 2005 autobiography Air Kiss & Tell that she was frequently visited by the “depression bogeyman”.
Dawson, 47, had long graced the pages of women’s gossip magazines and scenes in reality TV shows. Her modelling career had taken her to Italy, Britain and Germany during the 1980s.
New Zealand Prime Minister John Key tweeted he was “shocked and saddened” by the news of her death.
The Sun-Herald newspaper in Sydney reported that her body was found only minutes before her luxury waterside flat was due to be sold at auction.
The tragedy was discovered the day after the birthday of her former husband, Scott Miller, an Australian Olympic silver medal-winning swimmer who became addicted to the drug ice and accrued multiple convictions for illegal drug and firearm possession.
Dawson professed her enduring love for Miller and sadness at his fall from grace ahead of Australian 60 Minutes broadcasting an exclusive interview with him on February 16.
Kate Carnell, chief executive of Beyond Blue, a not-for-profit organisation promoting depression awareness, criticised Twitter for failing to sign up to an Australian government complaint-handling programme designed to remove hateful material from social media sites.
Facebook, Google, Yahoo and Microsoft signed up to the project last year.
“There’s lots more work that people like Twitter need to do,” Ms Carnell told The Sun-Herald.