Federal prosecutors said the couple used McDonnell's position to help Jonnie Williams Sr., former CEO of Star Scientific, boost one of his products. They documented more than $175,000 in loans from Williams and gifts that included designer clothing.
The governor and his children wept as the guilty verdicts were announced.
McDonnell, who testified in his own defense, suggested that anything done for Williams was entirely his wife's work. He said their marriage had broken down under the stress of his political ambitions, and that he and Maureen are now living apart.
His testimony, if the jury had accepted it, would have helped Maureen. Jurors were instructed that she was not a public official, meaning she could only be found guilty if she conspired with her husband.
The verdict appears to end McDonnell's political career, which included 14 years in the state legislature and a term as Virginia attorney general. He was indicted shortly after he stepped down as governor, following the single term allowed in Virginia.