Footage on social media showed eggs landing on the road beside the British monarch and his wife as they arrived for a traditional ceremony in York. They appeared to be unmoved by the incident and carried on with the engagement.
Police officers were seen in a video speaking to a member of the crowd, while others chanted "God save the king". Footage showed police carrying away a man in restraints to a nearby police van.
Charles, who came to the throne in September after the death of his mother Queen Elizabeth, is on a two-day tour of northern England.
Eggs were also thrown at Elizabeth's royal car in 2022 when she visited Nottingham, central England, and anti-British protesters threw eggs at Charles during a walkabout in central Dublin in 1995.
Reuters