The complex, set in 1,110 acres of East Sussex countryside provides 100 bedrooms alongside meeting and conference spaces for eight to 400 delegates as well as two championship golf courses.
East Sussex National owner Michael Hunt said: "De Vere were chosen ahead of other candidates because of their flexibility in adapting their requirements to suit the existing culture of each individual hotel and their emphasis on staff training and customer satisfaction."
Tony Dangerfield, chief executive of De Vere Venues, said East Sussex National was a 'real asset' to De Vere Venues expanding property portfolio which includes Heythrop Park, Chicheley Hall, Kassam Stadium, Studley Castle and Altitude London.
He said: “The new venues coming on board prove testament to our on-going growth strategy and our commitment to providing delegates with a diverse and varied selection of properties across the UK.”