Sixtus Leung and Yau Wai-ching of the Youngspiration party were arrested and questioned at a police station for several hours before being released on bail.
They told reporters they were charged with unlawful assembly and attempted forcible entry and must report to court on Friday.
The two young activists angered Hong Kong’s Beijing-backed government when they used their swearing-in ceremony in October to stage an apparent protest by inserting anti-China insults into their oaths.
Their attempts to enter the legislature during subsequent sessions to take their oaths properly descended into chaos when they were barred from the chamber while awaiting a court ruling, which later disqualified them from office.
Mr. Leung and Ms. Yau were part of a new wave of lawmakers advocating greater separation from the mainland who were newly elected to office in 2016 amid a rising tide of anti-China sentiment in Hong Kong, where fears are rising that Beijing is tightening its grip on the semi-autonomous city.
Three former assistants were also arrested. Mr. Leung said the charges, which relate to events on November 2, 2016, were “ridiculous”.
On that day, they scuffled with guards as they barged into the chamber, leaving the council session in disarray.
“We are still lawmakers at that time when we wanted to get into the chamber. Why is it unlawful?” he said.
The two said the charges were politically motivated.
“We are not afraid of this suppression and we will persist in our beliefs,” Ms. Yau said.
The Hong Kong government is pursuing cases against a number of other activists.
Last month police arrested nine people, including university professors, former student leaders and lawmakers, on public nuisance charges for their involvement in the “Umbrella Movement” protests. The 79-day movement ended more than two years ago after protesters failed to win concessions over electoral curbs.
The government is also trying to disqualify four other pro-democracy lawmakers who it says took their oaths improperly.
Individual cases include another lawmaker charged earlier this month with desecrating the Chinese and Hong Kong flags after he inverted some on the desks of pro-government members during one of the chamber’s chaotic sessions in 2016.
