The outspoken Democrat and former presidential candidate vigorously defended Jones, who resigned in the wake of criticism over his past statements and associations -- including his past support for a group that believes the Bush administration may have been involved in the Sept. 11 attacks.
"I think he was brought down," Dean told "FOX News Sunday," saying he just spoke to Jones. "I think it's a loss for the country."
Dean pointed to Jones' credentials as a Yale Law School graduate and best-selling author.
Though Jones signed a 2004 statement calling for an investigation into possible Bush administration involvement in the Sept. 11 attacks, Dean said Jones didn't realize what he was signing at the time.
"I don't think he really thinks the government had anything to do with causing 9/11," he said.
But 911Truth.org spokesman Mike Berger, whose group sponsored the statement, earlier told FOX News that Jones knew what he was signing.
Republicans swiftly called for Jones' resignation following the discovery that he signed the petition.