Bundy and others, including his brother and co-defendant Ryan Bundy, cast the 41-day occupation of the Malheur National Wildlife Refuge as a legitimate and patriotic act of civil disobedience. Prosecutors called it a lawless scheme to seize federal property by force.
In an emotional climax to the trial in U.S. District Court in Portland, Ammon Bundy's lawyer, Marcus Mumford, was tackled to the floor by U.S. marshals as he became involved in a heated verbal exchange with the judge over the terms of his client's release.
The verdict came hours after a newly reconstituted jury, with an alternate seated to replace one panelist dismissed over questions of bias on Wednesday, renewed deliberations in the case. Jurors previously had deliberated over three days.
The 12-member panel found the Bundy brothers and their four co-defendants - three men and a woman - not guilty of the most serious charge, conspiracy to impede federal officers through intimidation, threats or force.
That charge alone carried a maximum penalty of six years in prison.
The defendants also were unanimously acquitted of illegal possession of firearms in a federal facility and of theft of government property, except in the case of Ryan Bundy, for whom jurors deadlocked on the charge of theft.