The Hollywood star used his Toronto Film Festival press conference to condemn journalists for spreading the 'silly' story.
Rumours circulated that the Bourne Identity star had been killed after falling off the Palos Verdes Mountain in California.
Laughing off rumours: Matt Damon and co-star Scott Bakula at a news conference for The Informant! during the 34th Toronto International Film Festival yesterday
He said: 'My publicist got all of these phone calls from very reputable sources. I got forwarded the story, which, if you read it, it just gets sillier and sillier, and, by the end, the guy who's said to be my agent is quoting the lyrics to the Fresh Prince of Bel Air.
'And yet CNN called and The Boston Globe called, all of these reputable news sources are checking if it's true.
Alive and kicking: Matt with wife Luciana Barroso arrive on the red carpet for the screening of The Informant! yesterday
Matt is promoting his new movie, The Informant!, which premiered at the Venice film festival earlier this week
The star put on 30lbs of weight to play the role of business executive-turned-FBI whistleblower Mark Whitacre in the action thriller.
His latest guise is far cry from Matt's usual hunky persona, which saw him being named The Sexiest Man Alive by U.S. magazine People in 2007.
Matt admitted he had piled on the pounds 'mainly through pizza and beer' and said he enjoyed carrying the extra weight.
For the role he dresses as a geeky business executive, wearing metal-rimmed glasses and a caterpillar-like moustache.
Matt has reunited with Ocean's trilogy director Steven Soderbergh for the film, which has been adapted from Kurt Eichenwald's 2000 book The Informant: A True Story.
Mark Whitacre was President of the BioProducts Divison and Corporate Vice President of U.S. agricultural processor Archer Daniels Midland, when he informed the FBI the organisation had been meeting with rival companies to fix the price of the food additive lysine.
After spending three years working undercover for the FBI, he was eventually convicted for his role in the price-fixing and also plead guilty to fraud.
The film also stars Quantum Leap actor Scott Bakula and Back To The Future baddie Thomas F. Wilson and is set for release next year.
Mark Whitacre was President of the BioProducts Divison and Corporate Vice President of U.S. agricultural processor Archer Daniels Midland, when he informed the FBI the organisation had been meeting with rival companies to fix the price of the food additive lysine.
After spending three years working undercover for the FBI, he was eventually convicted for his role in the price-fixing and also plead guilty to fraud.
The film also stars Quantum Leap actor Scott Bakula and Back To The Future baddie Thomas F. Wilson and is set for release next year.