Corrine Brown, a former longtime United States representative from Florida, was convicted on Thursday of taking for herself thousands of dollars in donations that were meant to fund student scholarships.

Ms. Brown, 70, served in the House of Representatives for more than two decades and was one of the first African-Americans elected to Congress from Florida. But she lost her seat in a primary election in August, just weeks after she was indicted on federal conspiracy and fraud charges.

In all, a federal jury in Jacksonville, Fla., found Ms. Brown guilty on 18 of the 22 counts in an indictment that charged her with conspiring with others to run the fraudulent charity, filing false tax returns and other crimes, according to the Justice Department. She faces a lengthy prison term. No sentencing date has been set.

“Former Congresswoman Corrine Brown violated the public trust, the honor of her position and the integrity of the American system of government when she abused one of the most powerful positions in the nation for her own personal gain,” Kenneth A. Blanco, the acting assistant attorney general, said in a statement. “She shamefully deprived needy children of hundreds of thousands of dollars that could have helped with their education and improved their opportunities for advancement, and she lied to the I.R.S. and the American public about secret cash deposits into her personal bank accounts.”