English Landscapes will carry out a project to construct a new car park for visitors to the property, including associated soft landscaping and driveway alterations.
The contract — valued at £559,801 — is part of a major restoration project at Tyntesfield.
The National Trust originally bought the Victorian country house and estate in 2002 for £30m.
In 2006, it was granted £20m by the Heritage Lottery Fund to help with conservation and restoration work.
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