The Friends of Nonsuch was formed in 1991 to fight for the preservation of the Nonsuch Park Estate as an open space accessible to all. Their successful campaign highlighted the need for conservation work on the Grade II* Listed Georgian Mansion House and since 1991 groups of volunteers have been restoring the Mansion. The Friends also have groups researching the rich history of the site and are very much concerned with the conservation of the parklands and gardens of Nonsuch Park. The Friends opened the Service Wing Museum in 1993 which details the history of the site and also shows how a working service wing would have looked in the nineteenth century.

The Friends work closely with the Nonsuch Park Joint Management Committee who run the park on behalf of the London Borough of Sutton and Epsom & Ewell as well as the other inhabitants of the Mansion House and the users of the park to help ensure that the park and mansion house are protected and conserved.