Speaking after the verdict, Princess Hassa bint Salman's French lawyer said most of the declarations made by workman Ashraf Eid were false and that an appeal would be lodged.
According to the initial indictment, Ashraf Eid told police that the princess' bodyguard bound his hands, punched and kicked him and forced him to kiss the princess' feet after she accused him of filming her on his cell phone.
He told investigators his phone was forcibly taken from him and that as he was being beaten, Princess Hassa had treated him like a dog, telling him "you'll see how you speak to a princess, how you speak to the royal family."
Defense lawyer Emmanuel Moyne disputed the court's conclusions.
"There was no theft and moreover there was no violence. All the investigators' findings, the medical certificates demonstrate that the accusations made by Mr Eid are fanciful," Moyne told reporters.
The princess, 43, sister of Crown Prince Mohammed bin Salman, has consistently denied any wrongdoing through her lawyers. She was not in court for the verdict.
It was not immediately clear whether the ruling would complicate relations between Paris and Riyadh.
France has nurtured close ties with Saudi Arabia but those ties have been tested by President Emmanuel Macron's determination to salvage Iran's nuclear accord, which Saudi Arabia, alongside the United States, has adamantly opposed.
The Saudi government communications office did not immediately respond to a request for comment.
Saudi royalty has faced legal problems in France before.
In 2013, a French court ordered that the French assets of Saudi Princess Maha al-Sudairi, wife of former interior minister Prince Nayef bin Abdul Aziz, be seized over unpaid bills at a luxury hotel totalling almost 6 million euros ($6.7 million).