Many suspected the actor skipped red carpet to avoid more questions about his thoughts on Harvey Weinstein or sexual harassment.
The actor's father died on Dec. 14 after a hard battle with cancer, according to The Hollywood Reporter.
Kent Damon, who was 74, suffered from a rare blood disease and his condition had continued to worsen in recent months.
Damon was noticeably absent from the Los Angeles red carpet premiere of his new movie earlier this week, with the press largely suspecting it was a decision based on the backlash he's been receiving for comments on the sexual misconduct in Hollywood and some of the men who have been accused, or in the case of Louis C.K., confirmed the allegations were true.
Damon's father was diagnosed with his illness in 2010.
"It’s been a slow unfolding. My dad’s sick, so that’s a process we’re going through," the actor told Extra on Dec. 11. "We’ll take any prayers you got, so throw 'em up there."
"Downsizing," a sci-fi dramedy directing by Alexander Payne, hit theaters on Friday with just a 52 percent approval rating from critics counted on Rotten Tomatoes. To top it off, it has to compete with "Star Wars: The Last Jedi" at the box office, which will probably lead to more bad news for Matt Damon.