La Mare De Carteret fight: Two arrested and one injured
One person was taken to hospital and two people were arrested after "large-scale disorder" involving about 200 young people, police said.
The incident, which involved fighting, was reported at La Mare De Carteret playing fields at 17:50 BST on Sunday.
Parents of children who had attended a Cobo Balcony Gig at the nearby hotel were asked to collect them from the area.
A 21-year-old and a juvenile were arrested, Guernsey Police said.
They said one person was taken to hospital with minor injuries.