The five men from Cambridge, Banbury, Wolverhampton, Leicester and Stockport – and a woman from Banbury – were detained by police. All six are being held at a police station in the West Midlands.
Police said the suspects, aged between 21 and 37, were detained under Section 41 of the Terrorism Act. A number of properties are being searched in connection with the arrests.
In a statement, West Midlands Police said the arrests were “pre-planned and intelligence led,” and insisted there is no threat to public safety.
National Action became the UK’s first-ever neo-Nazi terrorist group to be banned in the UK when the government outlawed it in December 2016.