Barnett became one of the most recognizable figures in the 2021 attack after images circulated showing him with his feet propped up on a desk in then-House Speaker Nancy Pelosi's office.
Barnett profited from online fundraisers and even tried selling signed copies of the photos on social media.
He was convicted in January on all charges, including felonies for obstruction of an official proceeding and civil disorder as well as several misdemeanors.
In explaining his sentencing decision Wednesday, U.S. District Judge Christopher Cooper noted Barnett's lack of remorse, saying he didn't believe that Barnett was simply swept up in the rioting mob, as Barnett had testified.
"You were an active participant," Cooper said.
Leaning back in his chair -- and wearing a long white beard, gray suit jacket, silver tie and dark red shirt -- Barnett, 63, gazed back at the judge. When he was called forward for his final remarks before sentencing, he struck a mostly defiant tone but apologized for being "angry that day."