Police arrested 31 members of the group Patriot Front after they were found near the event, packed into the back of a U-Haul truck with riot gear.
Officers said they arrested the men after being tipped off by a local resident in the city of Coeur D’Alene who saw them getting into a lorry with masks and shields.
“They came to riot downtown,” said Coeur d’Alene Police Chief Lee White at a press conference, adding that riot gear and a smoke grenade were recovered from the lorry.
The tipster told police it “looked like a little army was loading up into the vehicle” in a hotel carpark, according to Mr White.
North Idaho Pride Alliance was holding the Pride in the Park event nearby where the men were intercepted by police.
31 men from at least 11 different US states were charged with conspiracy to riot, a misdemeanour. They went through the booking process on Saturday afternoon and are due to appear in court on Monday.
Evidence suggests the group were planning to riot in multiple areas of downtown Coeur d’Alene, not just the park.
Footage of the arrest has circulated on social media showing that men kneeling on the ground with their hands restrained behind their backs with zip-ties.
The men from the hate group were wearing matching navy blue shirts, khakis, camel Patriot Front caps and white balaclavas.
One man had the words “Reclaim America” written on the back of his shirt and another had “Victory or Death” on his cap.
Patriot Front was founded in 2017 after the Unite the Right rally in Charlottesville, Virginia, which left three people dead and many others injured.
The group calls for the formation of a white ethnostate in the US, according to the Southern Poverty Law Center, which tracks hate groups.