Specialist rural crime police officers are appealing for information after offenders climbed scaffolding and removed lead from the roof of the Temple of Victory in the grounds of Allerton Park, Flaxby, near Knaresborough some time between March 29 and 31.
The damage will cost thousands of pounds to repair, officers said.
The 18th-century Palladian-style building is Grade II* listed and is currently undergoing renovation. It is visible from the A168 and A1(M).
A spokesperson for North Yorkshire Police said: “North Yorkshire has thousands of heritage sites across the county – they’re part of the reason why it’s such an attractive place to live and visit.
"Our Rural Taskforce is working with partner agencies and the wider community to protect such sites, so that others can continue to enjoy them for many years to come.
“Repairing the damage caused to heritage assets is expensive, and the cost to communities can often be immeasurable. If you have an interest in heritage, or live near a historical site, please keep an eye out, and report any suspicious activity to us on 101, or 999 if a crime is in progress.”