The incident happened on Sunday night at Ballymena's People's Park.
Fencing would have to be erected around the multi-play area, said the mayor of Mid and East Antrim Borough Council, Audrey Wales.
She said the "mindless act" meant children would be denied the chance to use the equipment over the summer.
"It looks like the structure can not be repaired as the uprights have been badly burnt making it structurally unsafe," Ms Wales added.
"This pointless act of sheer vandalism has destroyed a very important resource for our children.
"As we are now into the brighter nights when children should be outside enjoying the park, this is particularly galling."
The council said most, if not all of the play area equipment would likely have to be demolished and replaced at a cost to the ratepayer.
"This is estimated to be a figure well in excess of Â£65,000 representing an unnecessary and added burden to the borough's ratepayers," said Ms Wales.
PSNI Inspector Doris Purvis said it was "an absolute shame" a play area that benefits so many local children had been damaged, and appealed for information about the incident.
Equipment at a County Antrim children's play park will have to be demolished after vandals caused more than Â£65,000 worth of fire damage.