John Burt was convicted on all five counts. The 66-year-old showed no emotion as he stood listening to the verdict. The judge ordered Burt held without bond pending sentencing.
He was charged with touching the girl on her breasts, groin and buttocks, forcing her hand to the crotch of his pants and writing her a note propositioning sex last year at a home for troubled teens he and his wife ran in Milton, Florida.
The girl testified over a satellite television link from Northern Ireland, where she now lives.
Jurors also heard from another girl who accused Burt of improperly touching her and masturbating in front of her although not charged with any crimes in her case.
Burt had associated with two men who committed anti-abortion murders in nearby Pensacola during the mid-1990s.