Mr. Sullivan, 29, of Tooele, Utah, did not receive the 87 months recommended by federal prosecutors for his role on Jan. 6. But his 72-month sentence was well beyond the 30 months his defense attorney recommended.

The sentence meted out on April 26 by U.S. District Judge Royce Lamberth brought to a close the more than three-year prosecution of Mr. Sullivan, one of the most recognizable Jan. 6 figures. He was arrested on Jan. 14, 2021—one of the first Jan. 6 suspects taken into custody by the FBI.

Judge Lamberth sentenced Mr. Sullivan to serve two years of supervised release after his prison term and ordered him to pay $2,520 in restitution and special assessments.

Mr. Sullivan came to the Jan. 6 events in Washington trailed by filmmaker Jade Sacker, who has since published a documentary about the liberal Mr. Sullivan and his conservative activist brother James.

Although media continue to report that Mr. Sullivan dressed as a Trump supporter on Jan. 6, that wasn't true. On Jan. 5, he posted a widely shared photo of himself to social media donned in a Trump ball cap. He did not wear Trump gear on Jan. 6.

Mr. Sullivan was found guilty by a District of Columbia jury in November 2023 of obstruction of an official proceeding, civil disorder and aiding and abetting, entering and remaining in a restricted building or grounds with a dangerous weapon, disorderly and disruptive conduct in a restricted building or grounds with a dangerous weapon, unlawful possession of a dangerous weapon on Capitol grounds, disorderly conduct in a restricted building or grounds, and parading, demonstrating, or picketing in a Capitol building.

Judge Lamberth denied Mr. Sullivan's motion for release from jail pending the U.S. Supreme Court's forthcoming decision on the constitutionality of the felony obstruction of an official proceeding charge used against at least 353 Jan. 6 defendants.