The man knocked two ancient busts off their pedestals in the museums’ Chiaramonti hall, which houses one of the world’s important collections of Roman portrait busts.
According to reports, the 65-year-old tourist allegedly told officials he wanted to see the Pope.
He was restrained by the museum’s staff and arrested by police swiftly after damaging the busts.
A source speaking to Reuters news agency said the man had “behaved strangely” and that the busts were damaged but not severely.
Italian media reports suggested it would cost €15,000 and take between 300 and 350 hours of work to restore the damaged sculptures.
Pictures taken by visitors and posted on social media showed the two broken busts lying on the marble floor.
The museums have begun welcoming tourists en-masse after easing Covid restrictions. They had received some six million visitors a year before the pandemic.
The most notorious assault on artwork in the Vatican was in 1972 when a Hungarian man jumped over a side altar in St. Peter’s Basilica and attacked Michelangelo’s Pieta with a sledgehammer.
He knocked off the Madonna’s left arm and chipped her nose and veil. The artwork is now kept behind bulletproof glass.