The actor told The Daily Caller that he believes Romney will win because of his "great talents", "great compassion" and "great gifts of leadership".
"The people are going to become aware of these qualities," he said.
"Now, what the other side has done is try to diminish all this - they've lied about him, they've done all this stuff trying to hide the true character of this man and the greatness of the fellow. Once people come to see that, they will be voting for him."
Voight - Angelina Jolie's father - also claimed that the media "has been taken over by this administration".
"It's not less than what has happened in Venezuela with Hugo Chávez, really, because you can't get the information through," he said. "I'm giving you this because I want to get the press my opinion. You can put it in any way you want to. But, it's become pure propaganda and we should be appalled."
Voight accused the "main media" of not covering the Republican convention in depth, saying: "They'll edit an hour - well, what will they edit out? What is the story they will tell?
"Guys, you should be appalled. America, guys, wake up. You should be appalled that they can get away with it, that they can attack - the Republican Party is a victim of a bias, of a destructive bias against the Republican Party. It's been going on all this time and it's getting worse and worse."
Voight previously defended Brad Pitt's mother after she penned a letter describing Obama as "a liberal who supports the killing of unborn babies and same-sex marriage".
Clint Eastwood and Jenna Jameson are among the other famous faces who have endorsed Romney, while Obama counts stars such as Eva Longoria, Morgan Freeman and Sarah Jessica Parker among his supporters.