Former school matron Tiny Virginia Makopo, 30, was accused of fondling and kissing more than a dozen girls at the talk show host's multimillion-dollar school. She was arrested in 2007.
"I will forever be proud of the nine girls who testified with the courage and conviction to be heard," Winfrey said in a statement today.
But Makopo was acquitted on all counts today, including charges that she also assaulted a student and a co-worker.
"The magistrate indicated that the state did not prove its case beyond reasonable doubt on all the charges. We won't be appealing the judgment," Mthunzi Mhaga, a spokesman for South Africa's National Prosecuting Authority, told The Associated Press today.
When the abuse allegations first became public, Winfrey, who has said that she was abused as a child, spoke out in support of the accusers. "They represent ... the new generation of youth in South Africa who fearlessly take back their voices to speak up about their concern for their fellow classmates," she told reporters, according to CNN.
Winfrey said today that students at the $40 million school, outside Johannesburg, are flourishing. "Our entire [Oprah Winfrey Leadership Academy] staff is committed to providing a nurturing educational environment so that all of our girls may continue to flourish. And they are indeed thriving," she said.
In March, Winfrey settled a defamation suit filed in Philadelphia by Nomvuyo Mzame, the school's former headmistress. Mzame claimed Winfrey defamed her in comments made after the school scandal broke. Terms of the settlement were not disclosed.