The gardens are considered to be the birthplace of the English Landscape Movement and have inspired gardens and parks around the world, including Central Park in New York.
Two full-time members of staff are employed on the contract, which started on April 1; a head gardener and an operative alongside seasonal and part-time workers. Gavin Jones has recruited from within.
No staff were put forward for TUPE transfer in the deal.
The Chiswick House and Gardens Trust was set up as a registered charity in April 2005 by English Heritage and the London Borough of Hounslow to oversee the restoration, management and protection of the site in south west London.
It features a Grade I listed villa and registered Grade I, 67ha acre gardens, a public park since 1929.
Trust director Clare O’Brien, said: "I am delighted to be working with Gavin Jones, as the Trust embarks on its next phase of estate management, with the aim of attracting more visitors to this important heritage house and gardens.
"One of the areas of the park we would like to develop is the use of the cricket pitch, for local companies as well as the local clubs. Gavin Jones’ experience in careful maintenance of cricket pitches will help us achieve this goal."
Gavin Jones' grounds maintenance portfolio includes Potters Fields Park, the Royal Palaces, and visitor destinations such as Bluewater shopping centre, Land Rover Experience and Mercedes-Benz World and English Heritage sites.