Voight introduced Romney at the event and posed for pictures with delegates, according to sightings on Twitter.
The actor, the father of Angelina Jolie, also attended the 2008 Republican National Convention in Minneapolis.
And he has ties to vice presidential candidate Paul Ryan. In 2009, Voight attended a major GOP fundraiser in Washington, where he was introduced by the Wisconsin lawmaker.
“One of the most courageous acts in our society today is to stand up in Hollywood and say you're a conservative Republican,” Ryan said of the actor.