The "Good Will Hunting" star was set to receive the Stanley Kubrik Britannia Award for Excellence at the BAFTA LA gala at the Beverly Hilton hotel, when he found out that his father Kent had taken ill.
A BAFTA member attending the party confirmed to the Daily Mail, saying, "Matt is not attending. We heard that he had a family crises and that his father was taken gravely ill. But we have not heard any more than that. A few people know but the majority of guests were not informed."
The "Bourne Identity" star later confirmed with a 20 second video clip, where he apologized for his absence and the late notice, citing personal issues and a "family emergency."
The Daily Mail also reported that the organizers of the show were contacted about Damon's news hours before the show. "He was one of the stars people were looking forward to seeing," continued the source.
Staff would not reveal any other details, as well as reps for the 47-year-old star have yet to comment to the Daily Mail.
Meanwhile, at the show, as the room waited for Damon to collect the coveted award in film, actress Kate Mara, who worked with Matt on "The Martian," let the crowd know that "Matt has urgently needed to travel back to Boston and is unable to join us tonight. And as much as we wish he was here, he has a family emergency."
She then added: "So our thoughts are with you Matt. And much love from your friends here in LA."
The brief video was then played with Matt appearing quite serious, according to the Daily Mail: "Hello and thank you everyone at BAFTA. I found out about this award six months ago and I was honored to receive it," said Damon, and then continued. "I was really looking to tonight, but I have to go back to Boston for a family emergency."
The actor then finished with: "I am really sorry not to be there tonight. Thank you for this wonderful honor. I hope you have a lovely evening. See you soon."
Mara accepted the award on behalf of Damon, whom she called a "legend."
Director's who've worked with the amazing talent that is Matt, like Stephen Soderbergh ("Behind the Candelabra") and Paul Greengrass ("The Bourne Supremeacy") praised the star, while close friend and confidant George Clooney painted him as a "sort of Jimmy Stewart," adding that he's "representing people at our best," as well as, "Matt is a writer in a real sense of the word."
Clooney also added: "He makes everything seem easy when it is far from that. You're a great friend, great talent…you're the best."
While it's uncertain as to how his father Kent had fallen ill, back in 2011, it was reported the he was battling multiple myeloma, which is a blood cancer that develops in bone marrow, however at the time E! reported that he was in remission.