"We found her guilty," government panel member Susil Premajayantha told reporters in Colombo after tabling the report in the legislature.
The parliamentary panel said it had found Bandaranayake guilty of three out of five charges of financial and professional misconduct brought by the ruling United People's Freedom Alliance.
The charges on which she was found guilty include failing to declare nine bank accounts and interfering in a case involving a company from which her sister had bought an apartment.
The panel cleared her, however, of stashing away $250,000 in an undeclared bank account.
The chief justice has said there is "not one iota of truth" to the charges.The panel said it had decided not to proceed with nine remaining accusations made by the Freedom Alliance last month because the guilty findings on the other "very serious charges" were sufficient to impeach her.
Under parliamentary procedure, if the chief justice is found guilty of even one charge, and a majority of the 225-member house votes for her removal, the president can dismiss her within a month.
The ruling party holds two-thirds of the house.
But the legality of the process used by the government to try to force out Bandaranayake is being challenged before the Supreme Court by the country's Bar Association which represents nearly all the nation's 11,000 lawyers.
A government minister, who asked not to be named, said the Supreme Court could still block Bandaranayake's impeachment by declaring her trial-by-parliament illegal, sparking a confrontation between the judiciary and the legislature.
A decision from the highest court, which has the sole authority to interpret the constitution, is expected next week.
"It is difficult to imagine the Supreme Court will just give in," the minister told AFP. "We can't rule out a major constitutional crisis. I think we are heading in that direction."
Another government member in the parliamentary panel, Nimal Siripala de Silva, said Bandaranayake had the option of resigning before she is kicked out.
"She can use this one-month period to step down on her own," de Silva said.
The move to impeach Bandaranayake came after she scuttled several bills, including one that gave more powers to President Mahinda Rajapakse's brother Basil, the economic development minister.
There was no immediate public comment from Bandaranayake.
A source close to Bandaranayake said she spent Saturday calling on Sri Lanka's top Buddhist monks in the central town of Kandy in a bid to get her side of the story across to the influential Buddhist constituency.
The US State Department has previously said it was "deeply concerned" about the impeachment process and urged Sri Lanka to "uphold the rule of law".