Zach Rehl was taken into custody at his Port Richmond home Wednesday morning.
Action News spoke to Rehl last summer outside a Trump, Pence rally in Northeast Philadelphia.
The Proud Boys are a right-wing extremist group that describes itself as "western chauvinists."
It's still unclear what charges Rehl is facing in connection with the January 6 attack on the Capitol.
SEE ALSO: 2 charged in assault of U.S. Capitol Police officer Brian Sicknick, who died after riot
Earlier this week, U.S. officials arrested and charged two men with assaulting U.S. Capitol Police officer Brian Sicknick with bear spray during the riot, but they do not know yet whether it caused the officer's death.
George Tanios, 39, of Morgantown, West Virginia, and Julian Khater, 32, of Pennsylvania, were arrested Sunday on an array of charges, including assaulting a federal officer with a dangerous weapon, conspiracy and other offenses. The idea that Sicknick died after being sprayed by a chemical irritant has emerged in recent weeks as a new theory in the case.
The arrests are the closest federal prosecutors have come to identifying and charging anyone associated with the deaths that happened during and after the riot. Five people died, including a woman who was shot by a police officer inside the Capitol.