The case dates back to 1987, when a 15-year-old black girl, Tawana Brawley, accused six white law enforcement officials of abducting and raping her, and of scrawling racist abuse on her body.
Rev Sharpton and the lawyers - Alton Maddox and C Vernon Mason - said one of the six was a former prosecutor, Steven Pagones.
But in 1988 a grand jury ruled that she had staged her own disappearance, and Mr Pagones sued for libel.
The libel jury will set damages later on Tuesday, although Mr Sharpton's lawyers have said they will appeal.
The eight-month libel hearing reawakened the racial tensions stirred up by the original case; a BBC correspondent says it sometimes degenerated into a shouting match, with lawyers trading accusations of racism.
Mr Pagones, who had demanded $395m in damages, welcomed the jury's decision but called it bittersweet.
"There is a lot of pain associated with this trial. A lot of wounds were opened," he said.
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