Work to transform Bretton Hall into a luxury 120-bed hotel and spa facility will begin in February.
Planning permission to convert the Grade II-listed building, in the grounds of the Yorkshire Sculpture Park, into a hotel and spa with restaurants, conference room and wedding facilities was granted in August 2014.
The council has agreed a contract with developer Rushbond Group who will carry out the work which will also include a new access road to the site.
Coun Denise Jeffery, cabinet member for regeneration, said: “The date being set for the start of the works is marvellous.
“We have been waiting for this for some time and now it’s finally going to happen.
“We are going to get a luxury hotel and spa in the district which is much needed because our tourism industry is booming with visitors coming from all over the world but they haven’t really had anywhere to stay.”