Colliers' Manchester office is handling the sale of Cheshire West and Chester Council's Backford Hall.
The site was home to 200 staff working in the highways, trading standards and waste management departments who should be out by the end of the year.
The council first announced the sale in May as part of a rationalisation of its estate.
The 24-acre estate at Backford, near Chester, has 100,000 sq ft of offices based around a 17,000 sq ft, Grade II-listed Jacobean mansion.
There's also a lodge, a stable block and a barn as well as woodland, 12 acres of farmland, a pond and boat house.
It has been reported that the council is looking for at least £2m but Colliers has not given a guide price.
Colliers director Mike Brassington said suitable alternative uses include residential, a hotel, or a retirement home. The council is offering it for sale on an informal tender basis.
Cheshire County Council bought the 40-room Backford Hall, with its galleried hall, mahogany staircase, twisted chimneys and ornamental ceilings in 1946 for just £10,000.