A jury member at a Tehran penal court told Press TV on Sunday that the news agency was found guilty of propagating against the Islamic Republic and disseminating false information to disturb public opinion.
The court is supposed to issue its ruling early next month. Reuters can appeal the verdict.
Reuters appeared in a court hearing in Tehran on Sunday after young Iranian girls training in Ninjutsu filed defamation charges against Reuters in February for describing them as killers-for-hire.
Reuters showed a number of Iranian girls training in martial arts in a city near Tehran, claiming Iran was training more than 3,000 female ninjas to kill any possible foreign invaders. The distorted Reuters report was picked up by other British media outlets.
The news agency also accused the Iranian government of training assassins.
The martial artists filed a lawsuit against Reuters shortly after the report became viral on the Internet.
The Iranian girls, accused by Reuters of being assassins, say the damage has already been done and they are now taking legal action against the agency for defamation of character.
Following the strong reaction of Iranian media to the report, Reuters made changes to parts of the report after a long delay. It refused to apologize for slander.