The demonstrators, 19 from Finland and 23 from Sweden, were held at Faslane Naval Base in western Scotland after blocking the main entrance Monday.
As home to Britain’s Trident nuclear submarine deterrent, Faslane is the venue for frequent anti-nuclear protests.
Several members of the group, all aged between 18 and 38, sat down in front of the gates and chained themselves together.
Group spokesman Martin Smedjeback, from Stockholm, Sweden, said the group felt compelled to travel to demonstrate at Faslane because it was their nearest nuclear weapons base.
“We believe that nuclear weapons should not be on this earth as they are a threat to humanity,” said Smedjeback, 33.
A spokesman for Strathclyde police confirmed that the group had been arrested over allegations of disorder.
The state prosecutor in nearby Dumbarton, Andrew Miller, told AFP that the group was not prosecuted.