The Holy Trinity Church in Longlevens, Gloucester, has closed after being targeted by three children on Thursday and Saturday, its vicar Rachel Forrest said.
She told the BBC that the church will re-open for services soon.
"They're messing about, but messing about like that can be really dangerous. It's the whole attitude of disrespect, not caring and thinking it's quite a laugh," she said.
The trio were caught in the act after they accidentally switched the church livestream on.
Gloucestershire Police has urged anyone with information about the incident to contact officers.
Ms Forrest said: "The really serious thing is people have been setting fire to things, so paper and palm crosses.
"In a building that's mostly wood with lots of curtains and flammable things around is really worrying.
"Loads of people have been popping in and saying 'are you alright? Can we do anything?'. A carpenter came in and asked 'do you need anything mended?'.
"That's lovely we've got the support of the community, and how appalled they've been at this."
A spokesperson for Gloucestershire Police said: "Police received a report that damage had been caused in a property on Church Road, Longlevens.
"The incident is believed to have happened between 14:00 and 17:00 BST on Thursday.
"A further incident of damage was reported to police on Saturday."