The protesters held the sit-ins on Tuesday to try to draw attention to Lieberman's opposition to the public option element of the national health care bill that the Senate will be voting on Congress.
U.S. Capitol Police arrested six protesters at Lieberman's office in Washington. Last week, nine were arrested there.
The protesters were asked to leave Lieberman's seventh-floor office but refused to go away, Sgt. Kimberly Schneider said. The protesters have been charged with unlawful entry.
"Senator Lieberman is getting paid by the insurance industry," she said.
Lieberman's office responded late Tuesday, saying: "The demonstrators insisted on disrupting office and building operations after they rejected repeated offers for meetings with senior members of the Senator's staff to discuss their concerns. After rejecting these meeting offers, refusing to heed warnings from the police and continuing the disruption, some of the demonstrators were removed by the police."